Yes -- just like they would diluted in the next round of investment. (And really, employees working for sub-market salaries in exchange for stock options are just another type of investor.)
But the founders get diluted too. In the no-pool case, the founders have 70% of the company post-investment, whereas in the 20%-pool case, the founders have 62.5% and get diluted down to 50% as the pool is handed out.
Ah. So the time of creation of the options pool doesn't matter, since eventually the founders get down to 50%. It's a matter of whether the options pool should be created in the first place.
But the founders get diluted too. In the no-pool case, the founders have 70% of the company post-investment, whereas in the 20%-pool case, the founders have 62.5% and get diluted down to 50% as the pool is handed out.