Personally, I don't condone the practice of leaving an aircraft running with no one at the controls. There have been some incidents of the aircraft sliding (one happended to an AS350 in Canada I think) from the unprepared landing site and ending up in the bottom of a valley.
However, I accept that it is standard practice in some places although I don't accept the reasons for having to do it. If you have to brief passengers, a shutdown or a ground crewman is a better option. If you have to pee, then you should have a proper break and stretch your legs and have some downtime.
In this case, the risk is potentially higher because the platform is basically unstable, ie. on pneumatic tyres. However, its hard to quantify numerically. It would probably be classed as a low probability but high consequence event.
I have recently witnessed a pilot leaving an aircraft running while he got out to fuel the aircraft while passengers were on board, not experienced passengers, tourists off on a sight seeing flight. To me, that is not acceptable because of the risk to the passengers.
HC, I take it that its not standard practice for both pilots to leave the controls while the aircraft is running on a helideck in Bristow (well not the UK part anyway but who knows about the GOM) If you don't see what all the fuss is about then what's wrong with one pilot going downstairs for a pee while the other pilot supervises the bag loading and refuelling? Although there are no control locks on a 332L or 225, surely you could fix a rope or something to the cyclic and tie it to the (uncrashworthy in some cases) seat?