Glad I checked to see if this weirdness had been reported, sad to see this was closed as "works as intended".
I can only assume this quirk is meant to mimic the impact of snow piling / distribution from prevailing winds of certain directions or something? Shame it just tends to look bad though.
For anyone else who comes across this, there is a mod on Modrinth that fixes this issue, named 'Steep Surface Fix', and given it seems unlikely for this to be reopened and officially patched, that's probably the best option for you.
After using a /fill command, I was wrong and debris does still generate. I still believe that it is significantly rarer though, I've attached images of my survival mine that outputted no debris whatsoever (apologies for low render distance, playing on a not great device)
Update: I did what Xarkenz suggested and did a comparison of the same seed in different versions, doesn't seem like there's a difference. Sorry for wasting everyone's time. I'll attach some screenshots of the test anyways.
I know of a server crash caused inexplicably by a custom pool feature in cherry groves, and I'm presently struggling with what I believe is a windswept custom pool feature crashing me, which is what led me here.
For me the crash was as Sniper1.1 mentioned, internal server appears to die and sends your game into limbo. Can't confirm if the cherry issue did that as well.