I think the difference in mining rates is less than the data suggest. For example, zerg at 9 o'clock gets 768 from patch 7 and 592 from patch 3 after 10 minutes. But you won't leave just one worker gathering for that time, you'll start with four and soon have more workers than patches. So what really matters is the mining rate from the top four patches at each base versus the bottom four patches, and even that will only apply until you get extra workers going.
This is still useful for telling you where to send the first workers and it might put you a couple seconds ahead in economy. That doesn't matter if your other skills are weak, but this does give an edge against someone who is otherwise matched with you.
I wonder if Blizzard knew about and intended the difference in mining rates between races. And I wonder if they're doing tests like these on Starcraft 2 to keep it balanced (or intentionally unbalanced in certain aspects).