Agreed! being able to sneak under a slab should stay, but being able to stand up inside the slab should go
(19w11b) Found some more:
Top faces:
Potted Cactus
Bottom faces:
The unpowered redstone torch-like parts on the Repeater and the Comparator, as well as the Repeater's 'lock'. Forget cullfacing, these simply shouldn't have bottom faces at all
Walls (if two walls are connected, and have another two connected walls on top of them, the bottom of the wall posts on top will not cullface)
Confirmed for 19w11b
I bet they won't fix it here because these textures are being made by Jappa, so they're really his responsibility. The only way to get this possibly fixed right now, is to bring it to his attention