When doing a cross reference for a bit-of-word, say D1000:12, all the references to that upper level element, in this case D1000, are listed in one group, sorted by location, so you get D1000:15 inputs and outputs mixed in with the :12 ones and so on.
For me I think it would be much more helpful if each bit got its own display group and label in the left column, or at least if still grouped by word/dword, that they were sorted by bit first and then by location. All the :0's first sorted by location, then all the :1's and so on.
If in separate groups, I'd have the D1000 native sized group first, then D1000:0, D1000:1 and so on.