The password is compressed into 256-bit key at the end so you gain nothing. Argon2 is used to derive the key, so all you need to worry is good password and maybe use keyfile if you want more security.

If you reach beyond 256 bits of entropy, there is no added security. No current system will use more than that. And going beyond that is not future proofing, because you're storing it in a current system, defeating any added entropy.

I don't see good reasons why you would use a password generator embedded in a password manager for non-security purposes. Security purposes here are always more important than other uses.

But if you do have a good example, feel free to prove me wrong.

Yes. Right now what you're asking for is useless nonsense, and your provided motivation is basically "But I want it" which puts you slightly lower priority than the little girl who wants a pony 'cos at least she can articulate why.