Eh, maybe, maybe not. What guarantees are there that the backups actually get deleted? Storage is cheap these days...

If you delete your remote backups, they are likely be deleted, eventually. If you don't delete your remote backups, they won't be deleted.

There's no business case for keeping backups around for Apple, unless they suddenly became an ad company and started mining your backups for personalization data.

There is a business case - charge the FBI or any government agency for the cost of restoring/delivering it to them, or use the contents to improve any machine learning they are conducting, and I'm sure there are others.

For the longest time Facebook couldn't actually delete photos that you requested the deletion of. They could remove it from indexes so it couldn't be found, but if you had the link it would still be available (akamai cdn). Because, to them, either the cost of the hosting was miniscule compared to the cost of writing the software to ensure things actually got purged from the CDN.

In the EU, big tech companies actually delete your data within a short period of you clicking the delete button because they're scared of the GDPR requirements.

Outside the EU, small companies, or non-tech companies might we'll keep it forever.