Yes. In addition, I wonder who in that organization benefits from the high-turnover of engineers. For example, in the question, the manager's boss had a theory

Yes. In addition, I wonder who in that organization benefits from the high-turnover of engineers. For example, in the question, the manager's boss had a theory that three new engineers were worth one seasoned one. Perhaps all of the seasoned engineers leaving is supporting his point, in a bizarre way.