One last try and then I give up.
It is up to eBid (not the user) to send the correct values for items in their feed to Google. To do that they must know what values to send. They have stated that they need to see EXEMPT placed in the UPI field of an eBid listing that has no UPI in order for them to know the correct value to send to Google.
So if Google needs to be fed false in that field to indicate there is no UPI, eBid needs to see EXEMPT entered into the field (i.e. eBid sees EXEMPT...eBid sends false to Google).
So what is entered in the UPI field of an eBid listing matters to nobody else but eBid.