I recently flew with Copa on a oneway trip via PTY, with a stopover in Panama for several days. I credited the first flight to TK.

At PTY, ahead of the second flight, I asked to change the frequent flyer number on my boarding pass so I could credit that flight to a different Star Alliance program. The Copa staff tried but told me that their system wouldn’t allow it and that it wasn’t possible to have different frequent flyer numbers on different flights within the same booking.

That’s a first for me. Is this just a Copa thing?