The bug
Despite being a block that can be immediately replaced by any other held block on right clock, minecraft:sculk_veins is not part of the block tag #minecraft:replaceable.
Gameplay impacts
Affects Enchanting tables causing them to blocked off levels
Any data pack which references the #replaceable tag will not have sculk veins included
How to reproduce
Find sculk veins
Inspect the tags that apply to them using F3
Replace them with a held block
Expected results
They would be replaced by the held block and be in #minecraft:replaceable.
Actual results
They are replaced by the held block, but are not members of #minecraft:replaceable, implying their replaceability is hardcoded.
Can confirm