Wither skeletons don't drop skulls

I killed 100 wither skeletons today on my server running 21w14a today and I got zero skulls with a Looting III netherite sword. Sure it is a 0.34% chance that this is a random fluke but it is 3 sigma, so getting close to Higgs Boson territory here. I got 3 skulls in my first 100-150 wither skeletons (didn't keep an exact count back then cause they kept dropping at least) on an earlier snapshot, so I'm tending to think it is not a fluke.

I could kill 40 more to get to 5 sigma.