I do agree with both HD and Dave, I think our interpretations of the rules are fairly similar, however the point which caught my interest was Joy Ride's initial query of "more and more Chinooks and Merlins ignoring the bends in the river... have [they] relaxed the corridor regs."
My thoughts were no they haven't, helicopters are expected to follow the routes as per the map regardless of type, but you're right, direct routing is definitely practised regularly as you say to avoid delays etc