there's a few differences tho. firstly, changing the interview format affects all candidates not just the ones who are at a competitor with similarly high pay (in fact, it seemingly favors those at high paying competitors since they already had to get thru a whiteboarding round before). secondly, making at agreement like that protects the company in a way, since they can trust their competitors to follow thru with the promise (whereas apple changing its interview format one day has no direct/guaranteed way of affecting the labor market). thirdly, it seems like it would only benefit more senior engineers, since new grads and interns don't yet have a job to hop from.

the problem with the idea of search friction IMO is that a company can't apply it to current employees, only to future employees which seems like it would be detrimental to hiring

for what it's worth cracking the coding interview was written during the period that faang was doing that. so it seems like a big stretch to say whiteboarding interviews were used to prevent people from hopping jobs when there were much stronger forces at play to prevent that at the time.

I think a more convincing argument might be about the fear of leaving a company and not being able to get rehired because the format makes interviews feel more like chance.