I suspect this practice would take the expected time from hire to productive from maybe 1-3 months to 1-3 years. This seems likely to be an expensive prospect,

I suspect this practice would take the expected time from hire to productive from maybe 1-3 months to 1-3 years. This seems likely to be an expensive prospect, and that's if we assume every single person makes a good engineer. Based on the comments of others, I suspect this approach is most useful in a business where you have positions at a variety of skill levels. In IT and tech, the base skillset required can be substantial.