confusion about LUKS encryption
Data is encrypted with Data Encryption Key. Each slot encrypts the DEK using a Key Encryption Key derived from a passphrase. Access to the DEK gets you the data. Access to any of the KEKs will give you access to the DEK. Clearing a passphrase slot, changing the passphrase, etc. does not change the DEK.

Whoever had access to the volume and a working passphrase could have extracted and saved the DEK, and that means they can use the DEK to decrypt the data in the future, when the slot with the passphrase they knew has been deleted. It also means they can decrypt any of the clones of the volume, even those for which the passphrase they knew was never valid.

If you really need to give different people access to a copy of the volume and be able to revoke access from other copies or from data added to the volume after their access was revoked, you have to change the DEK - reencrypt the volume or create a new encrypted volume (with possibly same passphrases protecting the new DEK) and copy all the data.

See https://crypto.stackexchange.com/a/24024

See https://security.stackexchange.com/a/205190/70830