I was just following the pattern we have here:
https://github.com/xtuple/xtuple/blob/4_5_x/enyo-client/database/source/xt/views/coheadinfo.sql#L191-L193

I agree with Gil, I could probably just return the id and uuid, but I don't know who's using the returning or why, so I just copied what the cohead view had.  The error happened when trying to save a new invoice.  It expected the uuid to be returns and without this change, it wasn't.

@gilmoskowitz 
What makes this different from the metric table is that this is an insert rule on a view.  Maybe that needs the full view structure to be returned.