If generally an employee stock option pool is ~5% of the company, then why is it worth spending time optimizing for that by firing people before stock vests? I suppose it'd be possible that management/investors view the employee ownership as getting out of hand, but even if the options pool is 10-15% (which I think would be fairly ridiculously large), it's likely mostly held by early employees who may have already vested.

It just seems like a silly thing to spend time doing, monitoring who will be vesting soon to fire them. Sure, maybe for one or two executives who are vesting integer percents of stock, but beyond that, it's not worth the time, and definitely not worth the backlash.