I'll preface this by saying that everyone should rate the way that they feel is right. I'm not claiming that what follows is objectively correct, but I do think it's important to consider.
Games released to the public don't have their reviews weighted by the size of their teams but by the quality of their work. It's not necessarily helpful to give leniency to someone because they had a small team or are inexperienced. We've all entered the jam under the same set terms and none of us have the same personal conditions.
There's at least one entry into the jam this year which someone was forced to get done in less than a day. It's super impressive that they were able to make anything at all, but I can't give them a five star rating in all categories due to their unfortunate circumstances. In my opinion that's not fair to the individual in question and it's not fair to every other person who happened to have more time to work on their own games or who was able to work as one member of a larger team.