Absolutely agreed. What's implicit here is the risk that somebody just won't work out. I once invested a huge amount of effort trying to train a junior dev and after 3 months he still didn't "get it". Not only was he unproductive but I was basically operating at half capacity for those three months. It was a huge exercise in frustration and something I will never attempt again.
I am sure that was very frustrating! Did you end up letting him go? It sounds loke the job wasn't a fit for his skillsets.
I will say that I have hired junior folks and seen them thrive after three months (take on more work with more autonomy) and that leveling up was so great to see. Plus it made them a better developer and more effective foe the company.
That's the flip side.
And it's not like a senior developer is a sure bet to be effective either (though I grant you they are, all things considered, a better bet).
I think this is the beauty of this approach as well (vs actively teaching skills). If somebody does not work out, you will know pretty early based on how they approach the learning in the first place.
