The new limit is based on a comprehensive evaluation of all aspects of life on an oil rig to include transportation to and from work. And it’s got nothing to do with the helicopters themselves.
If you want to know the reals reasons (and stop the baseless guessing and blaming), here’s the reason from the horse’s mouth:
https://www.youtube.com/watch?v=6QgwWQ_Pg3A
That video really explains it, I have only listened to a few minutes but it seems to be about the entire artificial environment, sort of like a space station, the aviation and transportation, the beds, the mattresses, the stairs, and I guess the 50 minutes will cover much more, it is a system and an environment and they want a range limitation in the humans they put into it.