(There is also the theory that there are gifted/ADHD/ASD traits which are all part of some much broader autistic spectrum than is currently believed, you may want to check out "bright not broken".)
That makes a lot of sense, given my family history and SO's. No one has gotten diagnosed with ASD but no one is really all that NT either. I see this outside my family too. I am working with a boy who is crazy advanced visually (he is 5 but functioning more like an advanced 8 year old - he is fascinating) but his older sib has ADHD.
Personally, it him it is the theory of mind-blindness that should be the ultimate test, not a collection of traits, and I do not think that parents should be forced to push for a premature, possibly inaccurate diagnosis simply to get their children services that schools or insurance might otherwise be unwilling to provide even though the functional impairment is clearly there.
In US, theoretically, it should be possible for schools to provide services based on functional needs but in practice, at least in my experiences, things don't move quickly unless there is a diagnosis. If I thought my DD needed services, I would rather go through our insurance so we can choose providers.
