Hm. Good question!
Try to use your best judgement here. Not everyone is open to extreme amounts of gore, but I personally will allow it for the jam.
The "No NSFW" rule is mainly for nudity and extremely grotesque graphic content. If the levels of gore aren't traumatizing, I think you're good.
Adding that disclaimer/warning at the beginning of the game, and/or the option to toggle it on/off, could be a good way to inform players and give them some choice before they dive in.
Hope this helped!