The behavior that Lightmap Encoding doesn't affect shadowmask textures is actually by design (albeit arguably a confusing design). Lightmap Encoding was originally intended to only affect reguar lightmaps and directional lightmaps, but only in some cases. This is not intuitive and we aim to address this issue by completely decoupling Lightmap Encoding from lightmap compression. Instead, we aim to add a new explicit lightmap compression setting in the Lighting Data Asset that gives the user full control of the compression quality used for _all_ lightmaps (including directional lightmaps, and shadowmasks). This removes a lot of edge case and simplifies the logic regarding how to configure lightmap compression.