Feature definitions are only loaded in a world when referenced from a feature rule or jigsaw (or any of their downstream children). This was effective for loading before, as features had no entry point other than those. Nowadays, commands and scripting can place freestanding features without their wrappers. As such, features desired to be used in those contexts without being bound to chunks/jigsaws must have no-op wrappers.

Reproduction

An attached world is provided for convenience. bug_features:glowstone is registered but cannot be placed via /place. This world can be opened (in Minecraft Preview) for inspection or unzipped to access the code associated with such.