The render call is executed at some asynchronous future time, e.g. when using rum browser-side it happens on a requestAnimationFrame. It's possible to receive e.g. a user-generated event or other unpredictable input that could remove a component before it has a chance to be rendered. I honestly haven't looked up or tested what would happen if code were to try to render something that wasn't there - presumably an error?

I wouldn't think removing the check would be in your best interest. Replacing isMounted with something current or better would seem to be the way to go. I've haven't looked up what that might be yet.

it looks like tonsky is pretty busy though. There's at least one good PR that's sat for a while.