I will look for the exact passage from LASORS tomorrow if I get a chance, but commone sense dictates that a single crew a/c only needs one pilot, therefore unless there is a specific reason, then how can two pilots log the time?
A holders operating capacity in this case can only be P1 or P/UT, not 50% of the P1 time because they happened to be sitting in the machine whilst the other pilot flew.
There were cases of people going out to the States and hiring a/c and both logging the time as P1, but eventually the CAA cottoned on to this and stamped on it as hard as they could.
This comes under the same thing.