Is this because the investors will exert considerable pressure on management not to give away many percentage points? But the theory is that managers, even knowing that, might be willing to sneak them in just before it closes?

Won't this leave you with a huge tax bill, since the differential between the strike price and market price is so great? Options aren't worth anything if you can't afford to exercise them, so might a slightly smaller percentage after an A-round actually be preferable in practical terms?