In a nutshell, yes, the maximum wind speed for a planned offshore startup or shutdown is 35kts for the S92, arguably this includes gust, which yesterday were quite severe.
The crew also need to consider the turbulence coming off the rig or is the deck sheltered from the wind. In yesterdays conditions they would make a dynamic risk assessment of whether shutting down or remaining rotors running is the safest option, they will always go for the safest option. If they elect to shutdown they need to consider how long they may be shutdown and if they can tie the blades down, this may require a working at height permit which can take time. If you have a technical issue and the rig has fuel, it will often be safer to remain rotors running while troubleshooting the issue and speaking to the engineers onshore.
Next time I would advise asking the pilots, they will always be willing to chat to the passengers about their decisions.