(Fabric 1.21.1) Negative-facing vertical slab has faces culled in situations where it shouldn't

[throckmorpheus]

The face is culled when placed up against a slab or stair (but notably not another vertical slab). It happens in X-facing and Z-facing orientations, but only to the slab facing the negative direction along that axis.

This happens on Fabric, but not NeoForge. I haven't tested versions other than 1.21.1.