This has been true for a long time with online award bookings. Here's a similar thread from 2005...
Duplicate(?) rooms when redeeming - which to choose?
The codes that the OP asked about in this other thread is known as the Room Type Code, I think. And I think that this is just a selection from a sequential list of codes that have been used to group all of the rooms into their different classifications. I don't that there is any consistent meaning of the codes from one property to the next, though.
I could be wrong, but my
understanding is that the hotels don't really follow these award assignments into ADA vs regular rooms. If they did, I would think that there would be a rash of complaints about how awards often get assigned irregular rooms. My
understanding is that the ADA classification is ignored for online awards. If that's true, I don't know how SPG handles ADA awards in which a customer actually needs an ADA room.
OTOH, my own experience is jaded by the fact that I usually expect to get upgraded to a non-standard room (or hopefully the best available standard room) anyway because of my Plat status. For non-elite members, I don't know if the room type assignment is usually left as is. If so, then these codes may be important. Unfortunately, there is some work involved to search the code in order to determine which room type is which at a particular property. One can, for example, usually find these same room type codes over in the paid reservations search area to match them up with their more detailed room descriptions.
I know that this question has been asked some other times, but I couldn't find the threads with my few search attempts.