A single-select or multi-select field in a Project or a Portfolio has Filter, Sort and Group options:
A reference field in a Project unfortunately does not currently have Filter, Sort or Group options:
But when that same reference field is added to a Portfolio, it has a Group and Sort 
Sort doesn’t seem to do anything, either ascending or descending 
And when I click on Group either ascending or descending, Asana crashes 
I suspect that both of these options should not be available in a Portfolio, although it would be great if they were.. and in projects!
Kindly asking the @Forum-team to escalate as a bug and confirm what the expected behaviour should be.
Thanks!