It seems to me to be fairly balanced. Don't forget that the humans also have the best home system. (and the 2:1 trade is pretty useful IMO)
Humans also benefit from an additional Ambassador slot and the ability to move three ships per action instead of two.
The Human advantages are not very apparent because of how the rulebook is written, but if you think of 3:1 trading and 2 moves per action as the "baseline" then it is pretty clear where humans are advantaged.