At the end of the day the engineer has a valuable skill and you're the one telling them they need to be more replaceable. You're the enemy. Of course you're going to think the tools that let you dehumanise your employees at scale are good things.
Maybe this is born from spending so many years in Amazon (with it's high turn over and near-quarterly re-org shuffling), but what's getting called "replaceable" here I'd call "writing maintainable software."
The goal is to get knowledge out of your head and into the codebase so everyone can reap the benefits. Knowledge hoarding is lame.