I also felt that the Hogue stock was lighter than wood or the factory hard synthetic. Is it possible the anal-obsessive guy who put that table together might have made a mistake?

I don't know if he had all those stocks on hand to weigh (wow...) or if he scoured the internet for all those statistics and then compiled them (just...wow...), but it would be easy for a typo or incorrect measurement to creep in there.
In any case, the difference in weight is not a large one, whether higher or lower. The increased comfort level of the Hogue stock is immeasurable but IMHO it makes it well worth swapping out for a Hogue.