Nobody is saying that they haven't made it work with or without the guy. The key here is that you're essentially saying their culture is OK because the end justify the means, but I don't think that's a company that I'd want to work for. If you do, that's fine, but having warnings like this are nice for the people who don't want to work in environments like that.

    you can build great relationships in a fast 
    paced environment with very senior and very 
    junior engineers thrown into the ring together.

Er.... yes, absolutely. I don't think that's being disputed. Certainly not by me.

I'm referring to the way it was done as described in his article. That is not a recipe for success. Or, at best: success achieved a lot less efficiently than it could have been.

I've mentored quite a few younger engineers and it has gone both successfully and poorly.

At a bare minimum, it requires a time and attention commitment from the mentor. Unless the job is so trivial (or the mentee so advanced) that the mentee can learn just by hanging around and watching.

When I was a dishwasher in a restaurant (hey, a fast paced environment) it was very easy to train the other new kids. I didn't exactly need advance notice. When I was a cook, it took a little longer. Engineering is slightly more complex.