Ahhh, this is all making sense to me now. It's because ClubWPT is technically a sweepstakes and not strictly a real money poker room. Florida does have some wonky sweepstakes rules that went into effect a few years ago, supposedly to protect consumers from scams. For example, there's a rule that says that
games of chance may be operated by commercial entities only on a limited and occasional basis (e.g. a couple months out of the year) as a marketing tool incidental to the sale of a product or service. Also, ClubWPT would have to register with the FL Department of Agriculture before each promotional period, pay a fee, supply a list of winners to the state, etc.
How do I know this? My wife is a part-time sweepstaker, and she's taught me a few of the rules.
Some additional information from their website (
https://www.clubwpt.com/prize-eligibility/) (emphasis added):
ClubWPT offers $100,000 in cash and prizes every month to eligible members. No purchase necessary to win. ClubWPT operates within the sweepstakes rules where they are legal and excludes people from joining who live in those states or territories where they are not. See Terms & Conditions for details and eligibility.