this isn't necessarily true. I haven't played in a while, but java servers using custom implementations like paper or bungeecord can use Geyser to allow Bedrock clients to connect to Java servers. There's some things that are wierd or don't work, as there's a bit of feature parity issues between versions, they're not the same game. But you can play together.

I used to play on a server with it and people would login with bedrock accounts (free with java purchase) so they could have an alt for dailies and storage.