This is a fascinating insight into a different world, thank you ! As an instructor and check pilot in lighter aircraft I was used to flying, teaching and commanding from either seat.. It was never specifically discussed or tested for, so the flexibility got quickly built in. Sure, if in doubt a quick familiarisation circuit with another instructor might be slotted in, to allow familiarisation with different control layouts or operating alternate handed, but not regulated for.
Actually the occasional variations added to the fun; when checking, say, survey or photographic pilots, they may prefer to operate from the RHS, so the instructor gets the LHS for a pleasant change !
Most interesting ; I didn't realise that aircraft captains might require approvals for flying in the other seat !