I dont believe this is the case at all, some of the best content on the market is Epics and alot of that is free… Making your own content is your own choice and workflow is part of game development it showcases a teams strength to work together in an integral manner which is important when you are judging how well teams perform.
Im sure instead of working on the game you could be planning on how to improve your workflow by limiting polygon counts, texture resolutions, I know people who avoid UV mapping or model smoothing to save time. There are a whole host of things a developer could draw from and balance in a way that suits the amount of time given, we have 7 days so its already alot more time than other jams.
I dont see why people reusing assets in interesting and creative ways should be punished because they didnt create the thing entirely from scratch. I would hope the GameJam would promote thinking outside the box whilst adhering to the theme, I think philosophy is a good alternative category and in the end we all want to have fun whether we are building or playing the games right? Why ruin peoples fun.
Also… WOW almost 100 teams :o