That's interesting, thanks for this insight!
I think it makes more sense to calculate the percentage of SP in bid bots compared to the total market = 21,240,294.1576 / (169,663,397.8027+21,240,294.1576)
or 21,240,294.1576 / total vested steem = 192,514,454 (from steemd.com)
which puts the percentage even a bit lower.
But I fear that the bots distribute a much larger part of the rewards pool, since they always vote with their SP while a lot of large SP holders (just take all the Steemit Inc accounts!) are not using their SP to vote.
Could you run some stats on how much of the rewards pool is distributed by bots?