Every single game on there is a 'real' game that was posted to the metaverse, which does not permit cheat codes or non-cosmetic mods. The data will be by definition skewed because it doesn't include non-metaverse games, which are the only way to play with functional mods and are probably the greater majority of games played. There are no records of non-metaverse games for GC2 (GC3 has better stats since it can track all games played).
Bear in mind also that the data spans all the way back to 1.0; there were strategies at various points that permitted very fast victories (spore rush, etc.) that were subsequently nerfed. At its peak, there was a big focus on getting the fastest military win possible on the biggest, highest difficulty map because that gave the highest score.