rick had it good...

It's kinda like the requirement for CFI groundschool... sometimes it just depends on the FSDO...may not be written, just understood as good practice... the examiner may look at your logbook beforehand and tell you he's not doing the ride (or worse, doesn't tell you but fails you for some reason)

I don't know why anyone wouldn't want to log time in the right seat with a person whose taken the same checkride giving instruction in the same aircraft for the checkride.