It doesn't really have to be. The issue that sometimes comes up, though, is the requirement for the applicant to taxi the aircraft/simulator (PTS requirement as I recall). The argument has been made that if the tiller is on the left side, the taxiing, at a minimum, should be done from that seat.

On a side note, my understanding is that some airlines are allowing their applicants to use rudder pedal steering to meet this requirement if the aircraft doesn't have a tiller at the right seat. I guess it all depends on what your POI signs off on.