There was no rule in this jam limiting the dev time of submissions to the duration of the jam. As a result, a small handful of the submissions were pulled from some peoples' backlogs of older, completed games. Sometimes with a few adjustments to better fit the theme, sometimes a straight repost. Again, there was nothing against the rules in doing that, but some people feel that repurposing a previously completed project like that goes against the spirit of a game jam, regardless of the rules.
Personally, even if there was a rule limiting dev time to the duration of the jam, I would not consider someone who had been messing around with learning how to make some mechanic/system/etc. and then applying what they've learned to put together a jam entry to be in violation of that. Otherwise, how far are we going to take that logic? Does the fact that I went into this jam already having a fair amount of experience developing in GameMaker give me an unfair advantage over someone who's trying it out for the first time?