We’re not folks that work Apple. We’re other users, like you. It’s no more “our” company than it is yours.
Apple is suggesting more iCloud storage because you’re using your current allotment. Renting more is an option, whether for photos or backups or otherwise.
When using iCloud Photos, any photos you delete from iCloud are deleted everywhere, on all devices. Either permanently after a month, or permanently if deleted from the recently-deleted album. Back up your photos elsewhere, and delete them.
Here is how to: Archive or make copies of the information you store in iCloud - Apple Support