I agree, I suspect that already there has been a not inconsiderable use of other peoples borrowed codes involved in group purchases. From watching that UEFA ticket transfer video, it clearly indicates that they can be forwarded/transferred via the App, presumably to any email that has a UEFA account!
In short, I am not certain that City will have back fed the email address of each code to UEFA, and therefore as long as the intended recipient has a UEFA account and the Ticket App downloaded, then they should be able to receive the ticket.
If however, City have backloaded code details of the code holder's email, then there could indeed be some seriously unhappy people who might not have access to tickets purchased on borrowed codes!