Eh. Their messaging is immature here, but you don't need to be on the biggest thing - especially when you have a limited set of contributiors, not millions.
It is deeply unfortunate that Git won instead of Mercurial and even more unfortunate that GitHub won. GitHub's code review/PR UI is an abomination. We had better tools 15 years ago and GitHub is still a regression. There are tons of reasons to move off it if you're willing to pay the cost of working with alternatives.
And I wonder why Codeberg and not a self-hosted Forgejo/Gitea instance? I also don’t like GitHub but this bandwagon to Codeberg doesn’t seem quite alright to me. There must be another way than jumping from one centralized git hosting service to another.
It is deeply unfortunate that Git won instead of Mercurial and even more unfortunate that GitHub won. GitHub's code review/PR UI is an abomination. We had better tools 15 years ago and GitHub is still a regression. There are tons of reasons to move off it if you're willing to pay the cost of working with alternatives.