Going back to the OP (original poster) question PIV needs their clients passports or passport images to negotiate on clients behalf with the airlines involved, so all goes smoothly when clients arrive. PIV cannot skimp on passport controls that exist.
Premium IV will email you, requesting certain information. You fill out information before you leave, giving Premium IV the information that they will ask for: your flights with numbers and the reservation confirmation number, pictures of your baggage so they can retrieve it for you at SXM (you don't handle your baggage; they find it for you and check it into Winair or whatever transport you choose to SBH, and they get you your boarding passes for Winair). Tried to find if I sent them a picture of my passport but have not yet found an email that I sent them with passport info..I'm not sure if they asked for that.
When you get to the terminal off your airplane, there will be a Premium IV Rep. with your name on a sign. You go through the VIP security line with an x ray machine for your carry ons in SXM with the Rep. in a special line. Then you handle your own passport when he leads you through to the Immigration window past all the other people but the Rep. is right by you. It is not in the regular line, of course. When you go through a private security line where they xray your carryons, you take off your shoes, so wear loafers or something without ties if you can..ties really slow you down. (DD got a knot in his..it wasn't pretty...

) ALSO, you do have to take off belt, watch, jewelry, keys, wallet, etc. that might set off the alarm, so put your stuff in your bag before going through the security thing. (Kind of disturbing when people are taking off their valuables and throwing them in plastic bins/bowls and putting them through the xray machine, but they are REALLY picky in SXM and obviously have different rules than the US, even in the VIP line.) Also, don't be in too much of a hurry and organize yourself and your belongings, and put your passport away right away, after immigration; it gets a little frenzied from time to time, and you do have to keep your passport safe; step aside for a moment if necessary. (OK, that is the "Mom" part of my travel speech

)!
You show your own passport upon arrival at SBH and they will stamp your passport and off you go to grab your luggage off the tiny carrousel and you bring it outside and the Premium IV people take it and put it in the van/car/whatever you are being transported in, or they take it to your villa or hand it off at your hotel to the bell person. Voilà!