(screenshot courtesy of @juliand665)

See https://github.com/LambdAurora/LambdaBetterGrass/blob/1.16/src/main/java/me/lambdaurora/lambdabettergrass/metadata/LBGCompiledLayerMetadata.java#L121 - LBG pushes a quad transform to move the snow layer to the right position, which isn't getting applied properly. Might require doing something with the MatrixStack in https://github.com/comp500/Indium/blob/master/src/main/java/link/infra/indium/mixin/sodium/MixinChunkRenderRebuildTask.java#L63

It turns out the QuadTransforms were fine, I just didn't apply the model offset at all...