Well, no it doesn't make sense, since that's not how pools work. A pool couldn't care less which miner actually finds the block for the pool. Shares simply represent the amount of pool work you have contributed. Your share proportion of the total shares the pool miners found for a "round" (pool finds block) is the proportion of the block reward you receive. If you're working with a high diff, and the pool finds a block before you submit it, that share you just found is credited to the next block found by the pool - it's not discarded or ignored. Solo and pool mining do not work the same, at all. When solo mining, you either find a block, or you don't; there are no "shares". Yes, there are solo mining proxies that use shares to measure your mining activity, but those shares are strictly cosmetic and have nothing to do with whether you find a block.
Edit: I over simplified some of this, and yes, you are correct that a share associated with the previous block will be a stale share, and yes, if you're diif is higher, it does, every so slightly, increase the chance of a stale share. On flypool, at a diff of 8000, I average 4000 shares an hour, and I typically see a rejected share once every couple of hours. So, I can't say that I see that as an issue.