The 120-hour rule applies to getting approved for entry to the Dutch side through SXM. You need a test within 72 hours to stay on the French side, or you’ll have to get tested when you arrive.

You can avoid testing again on the French side once you arrive if you have a PCR test within 72 hours before your departing flight to SXM or a rapid test within 48 hours before your flight. If you can’t do either of those, you’ll have to get tested for free on the French side within two days of getting to the island. We were able to avoid the second test by getting the PCR tests done the Monday morning before our Thursday flight.

All of this is supposed to be monitored by your hotel or rental host. Some have said they weren’t asked for the more recent test, but we were. I guess it just depends on where you’re staying. However, it’s supposed to be a requirement.