As an optimization to resource pack loading, everything in the relevant directory is compiled into this atlas, rather than only those sprites which are used by the game. For this specific atlas, there is no resulting visual change.
Beds have been changed to use normal block rendering, and thus their textures have been moved to blocks.png-atlas. However, beds.png-atlas is still generated in this version, albeit with only the missing texture present.[1]
Minecraft (until version 1.21.9) used to also generates mipmapped versions of this atlas, for unknown reasons. They are not used by the game at all - only blocks placed in the world which use the json model system use mipmapped textures.[3]
