Does uncollected "training" vault dwellers over time still max out the S.P.E.C.I.A.L perk?

Every time when i dont collect them for long periods of time (say 2-3 days), i come back to find all my dwellers being maxed out on the SPECIAL stat they were training on.

Now i open the game often, but every time i had to leave it for a few days i have noticed that this happens. Its possible that everyone was about to max out at the same time. But this world isnt perfect, and I cant be that lucky.

So, does the dweller continue training even if it was left unattended for extended periods? if thats the case, i can just dump a bunch of dwellers and leave them there over the 2-3 days (total time needed to max a SPECIAL), and come back just to switch them to a new room.

You need to collect each level.

So, if you leave them unattended for a few days, then everyone will have gained one level in the stat they are training.

I confirmed this by opening a vault I hadn't played in months, and seeing that many of my dwellers had improved a stat without maxing it.

Having everyone max out at the same time just means that they were all at the same level last time you played. Because of the increasing period each level takes, dwellers will tend to sync up their levels over time.