@Avoma.
Yes. When a mob or player dies near a sculk catalyst, some unknown process prevents the player from receiving experience orbs, a mysterious charge builds up in the nearby sculk in proportion to the amount of experience lost, and the code executes a mysterious replace blocks command very similar to the erstwhile ant program last seen in 21w14infinite. On the other hand, if a baby mob dies, nothing happens, because they don't drop experience orbs, and according to a recent bugfix, the sculk catalyst wasn't supposed to react when villagers turn into zombie villagers either [Edit: MC-250019]. Long story short, the sculk catalyst is supposed to absorb and transmit experience, and it's not doing that in three different ways. That's a bug. Just not your usual one.
@Anthony Cicinelli
Okay. If you think it's a feature, then I'm sure it's a feature. However, if I thought it was a feature, trust me, I wouldn't have posted it here. Looks like a bug to me.
@Sculk man
Sculk catalysts spread sculk blocks proportionally to the amount of experience orbs dropped by players and mobs. Unless there's a particular reason in lore why the sculk has to be exclusively carnivorous, my guess is this is a bug, caused by tracking the death of the mob, instead of the experience itself. Bottles o' enchanting are obtained from the same cleric villagers that buy up all the rotten flesh. Thanks for the reminder though–the sculk catalysts currently don't absorb experience dropped through mining ores, either.
This bug still affects 14w30c.
Confirmed for 14w29a and 14w29b.
Confirmed for 14w28a
@ampolive 'Unless there's a particular reason in lore why the sculk has to be exclusively carnivorous, my guess is this is a bug, caused by tracking the death of the mob, instead of the experience itself.' <—Me. You --> 'Sculk catalysts only convert experience through the death of mobs: it is specifically designed and coded like this; they don't convert experience gathered through other means, such as drops from ores, picking up items from furnaces, etc.'
Glad we're on the same page. It's a bug, caused by coding it in a hurry and hoping no one would notice, unless there's an in-lore reason why the experience generated by command blocks and bottles o' enchanting is different to the experience generated by spawning in the mob first.