When you "import" your content from Stack Exchange, you're actually just claiming content that's already here - when this site was set up, I imported the December 2019 data dump. That means two things:
- Any content you claim is already here. The owner is simply changed to your correct user account here.
- Any content you posted on SE since the 4th December 2019 will not be attached to your user account, because it's not here and can't be claimed.