There are only two states on yes/no (boolean) fields. Yes, or no. There is no empty.

When you create a new thing, or change a thing, if you set a yes/no field to empty, for all intents and purposes, you’re setting it to no.

You could create an Option Set with Yes/No/Empty and have RestrictedChapter? as an option set field.

Alternatively, you could have another field called RestrictedSet? which says whether the user has confirmed whether or not it’s a restricted chapter (whether
that be yes or no). Then, only include results where RestrictedSet? is yes and RestrictedChapter? is yes.

It’s a UX point I think Bubble should change, as, for example, these two settings are completely identical: