Phones should have a 'guest lock' feature

So…app pin?

The way the article talks about it, it is literally just app pinning. They also suggest only allowing guests to see select photos in your gallery when handing your phone which seems like more effort than its worth. Maybe just show your photos to people you trust?

fossify gallery allows to, hide photos and albums and to put a password on hidden item visibility. (other apps probably allow for similar use cases)

together with the app pinning that would be enough no?