Enable a toggle switch for enabling or disabling fuzzy match on Proton pass.

That will forces the manager to only show credentials that match the full app1.domain.com vs. app2.domain.com.

I know most users want their amazon.com login to work on smile.amazon.com or www. amazon.com without creating new entries. To achieve this, managers "fuzzy match" anything ending in the same main domain.

Having an on / off switch while saving the credential, will let you choose and indicate the password manager for which subdomains you kept the fuzzy match OFF and for which you kept it ON.
In this way it will be best of both worlds, convenience + usability.