It's not clear what he means by apply. I assume he means that they only ever applied for one or two jobs without having been recruited/having a connection to the company already. Of course in another sense, everyone applies for every job they've ever had, because there's always some sort of approval process for hiring.

I don't think he means that top 1% only ever worked at one or two companies because that's certainly not true (that or he and I have very different ideas about what kind of people the top 1% are).