When you bake an instance from Customisable Object Instance for Mutable asset - it looks like it converts existing bone sockets to - mesh sockets.
the function called is BuildMeshSockets() and it looks it takes the bone sockets as tags and creates mesh sockets for every existing bone socket.
It looks intentional, however we wonder why. What is the benefit of converting Bone Sockets to Mesh Sockets for mutable baked instances? Is it to improve performance?
We can just disable this function and it would not recreate the sockets, but first wanted to see if we are missing something.
Create a mutable Customisable Object Instance with a Skeleton that already has bone sockets to it. Once 'Bake Instance" the bone sockets will become mesh sockets.
When you merge meshes, you also merge in all of the possible sockets of the meshes defined by the skeleton or individual meshes. Object Group nodes can specify a socket merge at a higher priority, meaning that if you have an offset from a particular mesh branch, it will end with that one socket position. Mesh sockets, by their nature, allow you to override the positions of those defined on the skeleton, enabling you to customize the position of each that uses the same socket name. This also means that at the end of the pipe, the exported mesh will have those customized positions but will share the same skeleton for animation.
Imagine different chest pieces. You may have a predefined socket position for an attached pouch on the skeleton, but each chest piece overwrites that. When you use mutable, you can give the chest object group a higher priority to ensure that when a specific chest piece is equipped, the pouch socket is always in the proper position.
It is not recommended that you disable this function.
Thanks for the response Dustin. Yes, Mesh Socket make sense for all attachable chest assets and is quite neat to handle variation. Our concern derived from using Bone Sockets to attach props on hand grip bones. Sockets used for offset only, that would be the same across all meshes.
We will keep the convert Bone Sockets to Mesh sockets enabled as recommended.