No, we arrived yesterday, there is no quarantine. You need to get preauthorization from the EHAS website, and a negative covid test within a particular timeframe - which has changed from time to time., and was 120 hours as of yesterday. Once you arrive, you get a daily email asking you to report your temperature , but you are not quarantined.
Not sure what the "Sherpa" website is, but I would not trust anything it says!!! As barry said, no quarantine. There is no way to travel directly from the US to St. Martin. You just need to follow the rules for entry into Sint Maarten, and then once on island, you can travel back and forth with no issue. Anguilla has a quarantine, for sure, but again, no direct way from the US to Anguilla.
We are scheduled to return to SXM the end of May. We had our first Covid vaccine shot yesterday and should get our second shot March 19. I know the requirements keep changing periodically to enter SXM. Can someone post the website that gives the requirements so I can keep up with the changes.