It sounds as though that Marriott salesperson is trying to circumvent NY's timeshare sales registration laws, perhaps illegally.
Many states require a timeshare developer to file extensive registration info about a timeshare project before being approved to market timeshares to residents located in that state. NY has such a law. Even if you contacted Marriott first on this possible purchase, the law would likely still apply.
Thus, it appears that Marriott (or at least this salesperson) is willing to have you lie about where you live so as to flaunt the NY law. I don't know that you could get in trouble for doing so, but Marriott sure could.
NY also has a law that (as I recall) prohibits the developer from closing the sale until it can provide occupancy to you. Thus, if your purchase would be for part of the project that is still under construction, the salesperson might be trying to get around that law, again, perhaps illegally.
I don't believe Marriott condones such actions.
Incidentally, those registration laws don't apply if you are on site in St. Kitts making the purchase.