Okay it seems that already in 3.0 you can’t see through the model in weight paint mode… (even with all that settings) but i think because you can’t paint on the backside (or do you??) it doesn’t matter… even makes more sense to not show where you can’t paint… Or i didn’t get it…?
Yes, you can paint on back sides and it’s very helpful sometimes - if you uncheck “Front Faces Only” and switch Falloff Shape from “Sphere” to “Projected”: