When a user groups by a foreignkey column, it should show and sort by the value that's displayed in that column, NOT the underlying id value. I do have a workaround, but it seems like this is something that should be handled "out of the box".
I would be interested to hear your work around as well. This is an important feature for me as well. On one hand it is better to bind to the Item ID so when filtering for instance you send the ID (unique) instead of the name (possibly not unique) but then this makes grouping on those columns kind of useless...
What do you use for your workaround?