I think you’re missing the point as to why I might lose confidence. I’m fine with people being better than me, especially when they explain why they did certain things. But we work as a team, that means that before we do work, we agree on one thing. If suddenly an engineer decides a week later he wants to do something else, then that’s not cool. Even if he has a valid reason for it. Instead you talk to the team, and agree to change.
Again, there’s a reason why we work in teams, and not as individuals. I trust my teammates too, but rewriting code without any discussion breaks that trust for me.
You can discuss when the rewrite is done, that way it wastes less of your time: you can talk about non-hypothetical existing thing. If the discussion shows that the rewrite is bad then it's his problem: he has to fix or revert.
Plus even the initial rewrite is more time-consuming to do if he doesn't discuss it with the original author beforehand.
Again, there’s a reason why we work in teams, and not as individuals. I trust my teammates too, but rewriting code without any discussion breaks that trust for me.