They could - but why would they?

See my stats post for 1gh's potential revenue from their miners - ~$8.25/day given the parameters noted.

Compare that to rejecting solved blocks with 'too high' votes.  You mentioned accepting only votes <= 10.  In 1gh's case, that would leave ~19.86% of their votes.  ~$8.25 * ~19.86% ~= $1.64/day.  That's an immediate loss just from rejecting the other ~80.14%.  Say all of them will actually check out why their shares are being rejected, go to the website, and presumably read that the pool only accepts votes <= 10 - in reality, many miners won't even notice right away.  Let's also say all of them will adjust their vote and stay at 1gh, instead of the closer reality of just stopping HVC mining or hopping to a different pool.  The reward is eventually adjusted - let's say that's to 10.  Say 1gh does this at the worst possible time for payouts but best possible time for voting (as it's an average of 3600 blocks) and it takes ~5 days for that reward adjustment.  A new exchange rate would have to make up for 5*(~$8.25 - ~$1.64) ~= $33 lost.  The exchange rate would have to increase quite a bit.  They'd have to do so because they have a very strong belief that this will cause a sustained growth for the coin, and thus ultimately for them.  But that's really only just 'potentially', and with the waning popularity as it is ('+1 COMMUNITY EFFORT!'), that's a crapshoot at best.

If a pool wanted to play chicken with fate on this, I'd imagine they'd have to do this in a gradual fashion - rejecting an increasing % of those votes and starting at the high end.
Though at this point, pools are bleeding miners anyway, so maybe going cold turkey on it would make a good swan song