I've raised five kids to seven and, except for my Autism Spectrum Disorders (ASD) child, none ever routinely blurted non-related stuff to people at age seven.
Oh, ours did. Verbal diarrhoea on their favourite topic, regardless of what anyone else was talking about. It's typical of Autism Spectrum Disorders (ASD) kids to do this. Sometimes they are generally quiet and reserved unless you get them onto their favourite topic, when they won't shut up. In our house though, we have a couple who are outgoing and talkative, and when they have something they want to say, it comes out. Very random.
We have had to really work on difficult child 3, and continue to do so, to help him learn to NOT come out with random stuff. Example: I will be quietly working on my stuff in my room, difficult child 3 perhaps playing a computer game at the other end of the house. He will suddenly enter my room. "There's a funny line in X movie [quotes line - barely recognisable as he tries to tell me with his own brand of accent or other presentation]. Then he says something else, then she says this, then they go do something different."
I generally respond with, "Did I really need to know this right now?"
Or he will walk in and say, "If I push the left shoulder button while holding down the X key, it performs Y trick."
I respond with, "Am I ever likely to play that gam? Why are you telling me this?"
He continues with, "...and then if you go on to push the right shoulder button you can move the game to the next level where the character runs across the screen from left to right instead of right to left. Watch while it does this, you will see the character turn and wave." He then walks out of the room. I get back to my work, or try to. 45 seconds later difficult child 3 reappears. "...And then when the character has finished walking across the screen, it will turn and come back, this time with another character who normally wears a pink shirt but this time wears a blue one."
I start to say, "And you are telling me this because...?" but he has gone.
A minute later he reappears and again immediately begins talking. By this stage I am making a phone call to a business associate but difficult child 3 does not notice I am on the phone. He just begins talking. "The pink shirt comes back in the next scene, but only if you right click on the start key while you at the same time depress the X button."
If I wave at him and indicate I am on the phone, he does make an attempt to stop talking, but he can't help himself. He will back out of the room and lower his volume, but he will still keep talking because he cannot be interrupted. It is behaviour at an instinctive level (literally - I studied animal behaviour at uni). Instinctive behaviours are ones which, if interrupted, must still continue to completion. They are not under conscious control. A classic example is egg-rolling behaviour in broody hens. If you remove the egg partway through, the rolling behaviour continues even though there is no more egg to roll. In difficult child 3's case when he is talking at me, he can't simply stop when there is no more need to continue talking.
I also get this from husband, and from easy child 2/difficult child 2. Another example - they might begin to ask, "Have you seen the...?" when I have just watched them rummaging where we keep our keys. So if I interrupt with, "Have I seen your keys? Here they are, you left them on the bench," the Autism Spectrum Disorders (ASD) individual will still continue to completion with what they were saying, AFTER I have already answered their question. "...the keys for my car, they're not on their hook in the cupboard where they should be." They will say this while now holding the keys in their hand, that I just gave them.
Very frustrating, but there is NOTHING I can do that I haven't tried to do for years and years and years and... I am slowly going barmy.
This is classic Autism Spectrum Disorders (ASD) stuff. So is someone suddenly deciding to tell you about their pet topic, apparently purely at random. They also believe you are as passionate about the minutiae of their favourite topic as they are. They also believe that every image in their own mind; every association, every thought, is something you are equally privy to. It is a VERY difficult lesson for them to learn and it takes years longer than for most kids, because this is directly related to Theory of Mind.
You are at the beginning of a steep learning curve.
As for the fast diagnosis - sometimes it is obvious. I am not a doctor but I reckon I can identify Autism Spectrum Disorders (ASD) in seconds, in some cases. I am so familiar with it. Of course a more detailed evaluation is always a good idea for so many reasons. It can confirm a diagnosis, it can also give valuable information about the areas of need as well as the gifted areas in an individual's functioning. But a doctor who is familiar with Autism Spectrum Disorders (ASD) who spends enough time with your child to say, "This is Autism Spectrum Disorders (ASD)" - yes, it can happen and is still valid. Risky, but valid.
In our case, we had the kids assessed. Such assessments take time to organise (years, in our case) and in the meantime, we had a diagnosis we could use to get help. The assessment was actually more pessimistic than the initial diagnosis, in both boys. In other words the assessment not only confirmed the Autism Spectrum Disorders (ASD), it indicated it was more severe than we had known. However, we continued to work with the boys as if they were not so severe, were more capable. And presto! They became more capable. These kids will walk over hot coals to try to fit in, and to try to please you and meet your expectations. So if you expect good things, you have a better chance of getting them.
Positivity, love, support, compassion, will pay dividends.
Marg