Earlier quoted context omitted.
Basic math too. Suppose “ability” is normally distributed in the population and in your initial team too. Replace people when the new candidate improves the team’s median ability (supposedly what Amazon’s “Bar Raiser” checks). I kicked together a simulation of this process. The first replacement is pretty easy (50/50), but the hundredth hire on a team of ten often takes tens of thousands of interviews, and sometimes…
How many years does it take a team of 10 to get to their 100th hire? If they only replace 1 person a year, ~100 interviews a year sounds pretty normal to me (it actually sounds low compared to where I last worked where I sometimes interviewed multiple people a day).
It's also very vulnerable to "founder effects" if the teams are small: a few geniuses early on make it nearly impossible to hire someone new.