Just noticed that they (SXM ) have added some FAQ's to the stmaartenupdates.com site. (At least it is the first I have see them at the very bottom of page).
And with that new information I have an answer to my original question.

FAQ: How far in advance do I need to take my PCR COVID-19 test?
Answer: You can take the test at an earlier date as long as the date on the results are no older than 72 hours of your arrival day.

So it is the results date that needs to be 72 hours ahead of travel date.
That makes it a little easier to schedule the flight.
All depends on the turn time of the PCR test results in your area.

Hope this helps anyone else trying to travel.