Amazing concept, but I'm a little scared of getting exploited. Bare with my paranoia for a sec.
My opinion is that a Secret Santa might just join to get their game and they won't even work on yours.
The game you make by the end of the Jam is still YOUR game so you can post in on your itch.io personnale page and other persons than your giftee can play it, so don't worry if you don't recieve a game from your santa, you'll still be proud of you for the game you produced.
Really no reason to be paranoid about. This isn't a transaction after all. First of all you should remember that your Santa and your giftee are two different people. If you manage to make a game you do your part in make someone in the Santa chain happy. You get to keep the game, game making experience, game making fun, assets, professional help, discord friends and the warm fuzzy feeling that you did something good.
There will be people that wont finish their game for one reason or another. The organizers asked such participants to drop out officially, so you can get a new Santa from the Santa queue. Now if they drop out on the last day or simply don't deliver things get a little complicated. Since the submission is on the 20th of December it is technically possible for a couple of volunteer game developers to cobble together something small for you before Christmas. Not sure if something like this is planned by the jam organizers, but I would personally offer such a service to anyone without a gift. I will not see anyone ungifted!