Agreed with the rest, and also the last time there was a big jam like this, the itch.io servers had some trouble right at the deadline! It's supposed to be fixed, but I have a feeling this jam will test the limits.
For myself, I haven't uploaded a WebGL game before, so I want to get an early build uploaded ASAP to make sure everything works and I know what I'm doing! (I know it doesn't have to be WebGL, but it's a simple game and making it playable in the browser makes more sense and is probably more likely to get reviews.)