> this is a strong negative signal in the employees mindset, and a strong positive signal that there was a mistake in hiring

Agree that it's almost certainly a mistake in hiring but strongly disagree that it's a negative signal in the employees mindset

Being specialized in one area is actually a good thing for many people and many roles. It's actually kind of bullshit that software companies expect everyone to be a generalist nowadays

Having strong preferences about the tech you like to use and the way you like to build is fine. Find the employers with projects and teams that match your preferences rather than trying to crowbar yourself into everyone else's preferences