unsure if this is known, but if not, glad to help

I found, on bosses with cutscenes you cant skip i.e. azdaha, if you switch just before (might be frame perfect) the cutscene starts, you can do actions, but the boss is invulnerable. like in co-op. is this useful? kinda. you could set up support bursts like Bennett, or get a Zhongli shield, or more I couldn't think of

link of example:

This technique was widespread at least in the Ver1.X era. (This is because it can be used on Andrius.) It can be skipped cutscenes not only for switching characters, but also for ULT animation and Greatsword charged attack.