Just more of a check than anything.
Is there a way in a subassemblies to mate individual parts to different parts in the main assembly.
How I understand it you mate the entire sub assembly to main assembly.
What this is really about is more tidying up a assembly by have certain parts in a 'folder' like water fitting just in a water fittings subassembly instead of having a huge long assembly with everything in. But of cause this brings the problem of not being able to mate single items in the main assembly - unless I have missed something and there is a way to do this.