ALL new RR facilities to be accessible. Adding is new.
Existing facilities shall be made accessible to the maximum extent feasible.
Okay, let's make things really simple. Where does code, federal law, or other regulations (anything, I'll take literally anything) say
EXPLICITLY that EVERY SINGLE
NEW restroom needs to comply with the technical requirements of ADAS?
The language you provided earlier says that newly constructed or altered state or local government facilities must comply with the 2010 ADAS. I agree with this. However, that does not say all new restrooms, specifically, need to comply with ADAS Chapter 6. That is saying that anything new or altered needs to comply with whatever is in ADAS, and ADAS has the 50% exception in it.
ADAS Ch2 / CBC Ch11B Division 2 are the scoping requirements for construction. This chapter/division determines what is and is not required. This chapter/division explicitly states the 50% exception. Nowhere else in this chapter/division does it say that all new restrooms need to comply with the technical requirements of Chapter 6 / Division 6.
If 28 CFR 35.151 is broadly pointing to ADAS and not specifically pointing to the technical requirements, then it isn't saying what you say it's saying. All it's saying is that facilities comply with ADAS, and having 50% accessible restrooms meets the requirements of ADAS.
If there is something that explicitly contradicts this in code, that explicitly states that all new restrooms need to comply with the technical requirements of Ch6 / Division 6, please provide a reference for that. "Facility" is not explicitly defined as a restroom, and the definition allows for "all portions of a building". If the entire building is what a "facility" is, then having a new restroom that doesn't comply with the technical requirements (Ch6) but complies with the scoping requirements (Ch2) seems to meet code, both federally and in the state of California.
I'm not trying to be stubborn, but I personally need to see something that points to all new restrooms needing to comply with Ch6 and not ADAS in general. If I'm wrong then I'm wrong, but I'm failing to see how I'm wrong.
Again, what is the point of the 50% exception if it doesn't apply to new restrooms? Nothing in that code section mentions existing or new specifically, so it should apply to all single-user restrooms. If what you're telling us is correct, then every single new or altered restroom in any government building or place of public accommodation will need to be accessible, completely removing that 50% exception from being applicable to anything ever.