All miners produce diff 1 shares at the same speed relative to hashrate (let's ignore the variance there). They do this no matter what share difficulty is wanted by the pool. Every one of those shares has 1/pool_diff chance of being accepted by the pool. Saying "it would've taken 31 seconds to finally get that share, but because the block took only 30 seconds I never had a chance" is just blatantly wrong.
That doesn't make any sense. The whole point of a 512 diff rate is you send data to the server 1/512th of the time vs 1 diff. If they never get sent, how are they going to be accepted.