I intially thought that it was intentional that you couldnt collect the sculk flora which i tried to change, I started by changing the loot table via a datapack to just drop the item with shears but after checking it wouldnt drop. I then changed it to drop regardless of tool but when I broke them they still wouldnt drop anything. I then broke the blocks underneath them which made the item I chose drop from them. I checked and found that they were supposed to drop but they wouldnt for some reason. I found this on 1.20.1-0.9.23 version of the mod. The blocks affected seems to be diseased kelp, small sculk shroom and sculk shroom culture (both grasses drop fine). I tried this on a modded session with only Sculk Horde and its dependancies and this still was the case.

Another problem I found with them is that their in inventory/hand items are full sized blocks instead of being the same size as a regular items and blocks.

Thanks for the bug report, I'll look into resolving this.