Some thing would be lost, yes [1] but the core code and commit history would be preserved. Issues can still be re-opened if still relevant, and pull requests can still be seen in the commit history. Comments on pull requests, if not approving a pull, will result in additional commits to the code which will be preserved.
Whether this is OK for a given use case depends on how important ticket and pull request comment history is. For open source projects, I don’t consider that kind of history nearly as important as the code itself, since a lot of issues are wishlist requests, support requests, or downright spam.
[1] Including branches unless one runs a script to go to and clone each branch to the new repo
