Length of tenure is definitely not a good enough gauge.
I've worked with folks with 15+ years that could technically code but they took eons to deliver and their solutions were unmaintainable. Some of them with advanced degrees too.
Small sample size, but the few folks I'm thinking of were such bad hires that could have been avoided if we had them write some code or put the proper emphasis on the coding exercise we had them do.
But being a slow worker is going to be revealed during a whiteboard coding test?
All small programs are maintainable, no interview process will tell you if a developer can deliver large, complex programs that are clean, modularized and easy to maintain because there's no time to do something of the requisite size.
It's true there are experienced devs who suck, but that doesn't mean whiteboard coding is the process that filters them out.
I've worked with folks with 15+ years that could technically code but they took eons to deliver and their solutions were unmaintainable. Some of them with advanced degrees too.
Small sample size, but the few folks I'm thinking of were such bad hires that could have been avoided if we had them write some code or put the proper emphasis on the coding exercise we had them do.