I guess I don't get it. This Ph.D candidate was recommended by the previous CTO and was the one spearheading the framework transition...and then was fired after 2 weeks? But junior devs at the previous firm were given months to get up to speed?
Perhaps the guy felt he was going to get a raw deal and so was spending the few weeks looking for another job? Who knows. Lots of potential variables that might have turned an otherwise stellar coder into a quivering mess. The plural of anecdote != data.
It's quite possible that I could judge someone at some task (say cutting & laying intricate tiles), and think they're quite good. They may seem fast to me because they're doing something that would take me forever. But if you brought in a real professional, they may laugh and say worker is going to slow.
The author said that the coder in question didn't show any improvement after 2 weeks of coaching. The developers at the previous firm he mentioned were slowly improving, that's why he kept them. From my reading I got the impression that if the PhD candidate had improved, he would still be there.
New Dev hired by the CEO without input from anyone else. She was not bad, but terribly sloooooooooooooooow. She indeed took 10x longer to do common tasks compared to other devs.
It's not that she wasn't smart or reticent to learn new things, just that her way of working through problems was incredibly long winded for some reason.
It's not something that you can easily re-train someone to fix, it's a fundamental problem and that combined with other issues made us let her go.