I imagine the database corruption prevented the permanent delete from the Recently Deleted folder that's supposed to happen 30 days after you mark something as deleted.
If it behaves anything like the Mac Photos app, then it's using hard links for things like importing photos which can lead to bugs like this if the corruption led to them losing track of one of the hard links, since you have to delete all of them to actually delete the file.
That’s a reasonable explanation. Still, they need to be a lot more transparent about what happened and confirm explicitly that those files are deleted now and that in general, files are permanently deleted. I feel like all too often, Apple just stays silent on issues and avoids any semblance of customer support, and that needs to change.
If it behaves anything like the Mac Photos app, then it's using hard links for things like importing photos which can lead to bugs like this if the corruption led to them losing track of one of the hard links, since you have to delete all of them to actually delete the file.