I'm confused how that could work. Let's take the same employee but have them leave the company, executing their options, just before Hooli acquires them. How do they end up vesting at all?
Are you saying: the vesting schedule on your as-yet unvested stock might reset when the company is acquired?
How often does that happen? How often does the exact opposite thing happen --- accelerated vesting on change of control? Because that other thing also happens.