Can't play PS5 version of the game without buying another copy?

[BenjagoCrowe]

Sorry, but your friend is incorrect. You have to buy the game (and expansions) for each platform that you want to play on.

One slight upside though is that for each new platform you get 30 days free so that's something at least.

There's your answer. The only free version of PS5 is if you're upgrading from the PS4 version.