Expected:
A bundle can hold 64 bee nests/hives regardless of there being bees inside.

Actual:
A bundle only holds a single bee nest/hive if there's 1 or more bees inside.
A bundle holds 64 bee nests/hives if they are empty.

Reasons why this behavior is a bug:

• The change was not in the changelog, previously 21w19a and before? (Certainly in the snapshot that introduced bundles) It was possible to hold 64 bee hives/nests regardless of bee contents.
• It also defies the rules that bundles follow: "Otherwise stackable blocks or items can be bundled up to their respective stack size", even bee hives with bees inside could theoretically be stacked (middle ctrl+click in creative to get a stack of NBT hives) Although unlikely, it is possible and therefore goes against this logic.
• Other NBT items like filled maps are allowed stacked to their stack limit inside of bundles

It also affects the usefulness of a bundle.

Attachments include difference between bee nests in same version 21w20a and how treasure maps behave in bundles.