I think it depends on a variety of factors, mostly which type of testers you get. For example, I suspect that game jams with public voting get a higher rate of careless reviewers (and ironically, you may get a higher share of them with a navigator version, because they would not have played your game otherwise!). I reviewed games for GMTK 2022, and I know I thought some games received a harsh treatment, or some games ended up placing incoherently relatively to one on another on some specific criterion in my eyes.

By the way, is the rating in the current game jam closed to the public? I do hope so, seeing what I wrote above! X)

PS: about the type of testers you receive: in the same vein, I also think this depends highly on how they find your game. If they find it randomly, they may be harsher. If they came through a least rated or Karma ordering, they are more likely to be caring people and be fair. If they came from a comment of yours under their own games, they may also be more willing to give fair attention to your game.
These are just my intuitions, but this sounds like common sense.