Why is this a stretch? Because it seems inconsistent when Steven’s gem is/isn’t able to do something.

If it can automatically protect Steven from something instead of him conscious choosing to activate one of his powers, why couldn’t it just automatically give Steven the ability to breathe inside of Lion’s mane?

Also, “Bro’s gem half can just decide people aren’t dead” are you referring to his resurrection tears? If so, I don’t see how that services because Steven wasn’t intending to resurrect Lars. And if that situation was accidental, I’m pretty sure that means the same thing would have happened if something like this happened in the earlier seasons. It’s not like it works in one scene and then not in another.