As long as the specific warnings are at the forefront, I think that could be fine. When I'm trying to avoid certain content for my kids, or even for myself when I don't have the spoons to deal with a certain topic, knowing the content matters a lot more than the age rating imo
There's some PG-13 movies that I'm perfectly fine with my 5 year old watching alone and there's some PG and G rated films (Jaws, Poltergeist, Watership Down, etc.) that are just too much, so I'm sure it'll work the same with self rated E/MA/AO. For me, the warnings matter more than the rating itself.