"Disable new downloads & purchases" does not seem to work as intended if a game is included in a game jam.
I selected "Disable new downloads & purchases" for one of my games and this made the files unavailable on the game page specifically, but for some reason, they remain downloadable from the game jam submission page.
The wording of "Disable new downloads & purchases" suggests to me that downloads would also be unavailable even from the submission page of a game jam the game was submitted to.
For now, I've made the files hidden so that they are not downloadable by anybody, but ideally I would like to be able to keep them available for people who already own the game or get a download key only, as the text explanation for "Disable new downloads & purchases" suggests.