You would keep a list of unique identifiers (opaque) that were deleted and filter data out prior to rewriting/restoring it. It’s cumbersome but not impossible.
So I need to keep a list of people to delete from my backups when I restore them? Is keeping that list even GDPR compliant?
The gist seems, if you are sticking your fingers into your ears hard enough and shouting loud enough, it should count, maybe, in at least most European nations.
But remember, strictest interpretation wins.
So you then need to make sure that dataset is at least as resilient as your cold backups. That's not exactly a trivial problem in most cases.