I've wondered occasionally if we should have advocated for DD to take the SAT/ACT in 7th, but my research on the subject uncovered what you mention-- that below a certain age, it really doesn't unlock much of anything, PG or not.
Our experience was exactly opposite of that. Without scores we could have used dynamite and not been able to cross through the college admissions door with a preteen. With the scores - open sesame! So, I would encourage anyone who thinks college is needed for their child to go ahead and try the SAT or ACT. We had zero problems with registering for either. The ACT has allowed registration online. The SAT will send you a registration packet by mail. And, of course there is always the option of registering through talent search but it is more expensive and less flexible on dates.
As far as accommodations, I agree it is a process and you need to allow time for that process. That is true no matter your child's age. If your child has a medical condition where they can't be apart from you or a person who has been trained in medical procedures probably you aren't thinking about registering them for independent college experiences at this point. So, I would guess it probably isn't something to worry about right now.
