I get a big laugh when I see a DX spot with "up" as part of the callsign. I guess if you think "up" is part of the callsign there's no reason to operate split. In the world of the DX clusters it certainly provides for some comic relief.
I have often wondered about a similar situation.
Some years ago there was a popular DX with the call K5DUP.
I had been listening to 7.023 for over an hour. There was this station with the callsign K5DUP. Very loud. Lots of people calling him. However, the caller could not hear them. Every call that K5DUP answered was a station I didn't hear. Every station I could hear was seemingly ignored. Propagation?
Also lots of different signals just sending their last 2, and in every case those last 2 are UP. What an Astronomic coincidence that so many callsigns end in UP. If the DX were to come back to them, which one would know to answer?
Maybe he moved down to 7.023 because of all the noise (solid wall of signals) extending all the way from 7.025 up past 7.035. Was there some kind of contest going on up there, or what?