As other posters already mentioned, DAS has nothing to do with dining. It is only used for attractions at the Theme Parks and provides the ability to wait outside of lines.
The advice the Dining CM gave you was partly correct.
Some of the dinner shows have specific areas for guests who are using mobility devices (
ECV, wheelchair).
The 2 specific ones I can think of are Hoop de Do Review and the Spirit of Aloha Dinner Show. Since those are specific shows and have limited numbers of accessible spots for each show, you do need to reserve an accessible spot/table.
The only character meal that would be any issue would be Cinderella’s Royal Table, where some of the tables are down a step. For
that character meal, it would be a good idea to have it noted if you have a mobility device. Because the restaurant is accessed by a small elevator (or a set of stairs), there
may be limits on the number of guests who would need to be evacuated by the fire department in case of emergency.
But, they could still accommodate you there even if you ONLY tell the CM you have a mobility device when you check in.
There are no other character dining locations where guests with disabilities need to be in specific seating. The Dining CM was incorrect about that. Again, even if you just told the CM when check in for your ADR, they can still accommodate you.