The ToT mod issues official community challenges, but otherwise it's the same system of an unofficial treatless spreadsheet and participants/other interested parties banding together to try to make it happen. There's still a week between the due date and reveals.

I have a few hypotheses, and any or all of these could be partial factors in the difference:

-Chocolate Box's higher signup count means there's proportionally more casual participants compared to hardcore treaters

-Also it's just harder to organize shit with nearly double the number of people

-Trick or Treat's character-based OR matching means the participant pool self-selects for people who are more flexible about what they can write and draw, and what they want to receive - means they're both easier to treat + have an easier time treating

-Something about the time of year, both in terms of their spots in the exchange schedule (people burned out after YT? ToT takes advantage of a clearer schedule? more casual participants finding Chocobox via YT, whereas in the fall, YT newbies are too late to sign up for ToT?) + general life patterns (maybe more people working on theses in spring semester?)

(standard disclaimer that this is only comparing treating rates. Both exchanges have their advantages, and I love both a lot.)