Prefer explicit methods over delegates for predicates

What does this MR do?

Predicate methods should return a boolean value, however when we delegate with allow_nil to properly handle non-extant relations, we end up with true, false, and nil as possible responses. While we generally are loose about nil being equivalent to false in Ruby, I feel like a predicate method is a special signal that we very much care about the boolean-nature of its response.

Related to !54262 (merged)