No, WiFi or your cheap local home router do not play into this. The only possible interpretation is that Google Fiber allows netflix to on average deliver higher bitrates compared to competitors. The reason you don't see higher speeds is because there is no point in streaming at a higher bandwidth than the content actually offers.

All in all, these are terribly misleading statistics. At best, they suggest that Googles competitors can't get their shit together to even allow for one HD stream.