Depends what his status was in the company.. if he with his low time in type is restricted to the RHS per their 135 ops manual, then thats were he will sit and fly.. just because you are PIC rated in a 91 sense doesnt give you right to sit in the left seat for 135. In my 135 and previous EASA AOC ops, we dont allow F/Os to fly from left until more experienced, as there is no tiller in the RH so you as PIC cant do nuthin if they decide to clip a wing going in and out of crowded FBO ramps.. My experience is also many Captains feel very uncomfortable acting as PM from the Left.. with handover of controls and taking them back after landing on the roll out.