If a feeding slab is placed into flowing honey, then it will turn the flowing honey into a source block which can then be bucketed by the player.

second minor issue:
The honey-logged feeding slab also doesn't update and flow out from the sides except when honey is first placed.
You can recreate this by honey-logging the feeding slab and letting it flow out, then blocking the flow. When you remove the blocks you just placed the honey won't flow out again.