Good Question and good points.....short answer.......we do not have the information and details to answer it.
The one mistake RCCL did make is sending out that notice that the storm was worse then they expected. That set the whole weather *guessers* as you put, it in a up roar, because they were predicting 100 mile an hour winds on Friday and they have the proof in the reports. That raised questions in some peoples minds of a cover up.
You are also right that winds in a storm circulation like that massive ones vary easily from 50 MPH to 100 MPH.
As I have said before, I will not 2nd guess the Master, and no one else here should either., I don't have the details of the weather reports he had. As you said, where was it 50 mph winds and where it was 100 mph, the track of the storm etc. We also don't now where he was and when and how the vessel was handling the weather. From what I have seen and hread, the Master is a great job in handling his vessel in severe weather conditions.
Just because there is a really bad storm out there, doesn't mean the Master should not have sailed. What I saw of his chart and he had a plan, but the storm beat him to the punch. It was a rough place with the coastal USA sitting there, limiting his choices.
As to was it RCCL fault if the weather changed?..................The Master is responsible for his vessel, it was his decision in the end whether to sail or not and where to go. If his actions were prudent, based on good principals of seamanship and the conditions,....No he was not at fault, neither the Master or RCCL was at fault. Now if he sailed just to complete the cruise and did not act prudently..........then both he and RCCL have some problems.
I will say this, I do not believe the Master sailed just to complete the cruise.
I hope this made sense
AKK