That's an awful comparison.

It's like email.

You can have a gmail.com address, and send and receive emails between yahoo.com and hotmail.com addresses without issues. Nobody really cares which provider you chose, and if you really want to, you can register your own domain and host email yourself.

If this doesn't land, then the person you're talking to probably has never used a computer.

But they are just different entraces to the same "public square": the fediverse