...they don't literally mean "luck", except to express that there is variance. They're using the word to mean bad results, happening more often in ex-google employees. And that's not BS at all.

They don't have to use the word or mention it at all because bad results are already implied by the context. The reader already gathers as much.

Mentioning the word luck draws it in a different light, as if next time the odds might be on their end. Luck is meaningless if there's enough skill. Its an overused (if not downright abused) word.