Quark. Also goes by Charm.

I wouldn’t call it a feature since this is the standard behavior used throughout the system. This includes the example you provided, where Photos will offer you to input the passcode after a few Face ID failures for the hidden album (just tested this). Even arguably much more sensitive functions like Apple Pay payments fall back to the passcode. Those family members can already access all those hidden areas anyway, with the exception of apps that have their own PINs/passwords behind Face ID