There’s not so much ‘receiving” as “sharing”, and the connection is bi-directional, and a new photo loaded anywhere is loaded everywhere, and a deletion anywhere is a deletion everywhere.
iCloud is a synchronization service.
There are other iCloud-associated synchronization services; this bi-directional sharing (of additions, changes, and deletions) is not limited to Photos.
If you have sensitive data, use a separate Apple ID.
Maybe with Family Sharing and shared albums enabled.
Similar for cases with multiple people (mistakenly) sharing the same Apple ID. Migrate to separate Apple IDs, and enable Family Sharing.