> Doing a refactoring of some basic Java code that's not going crazy with annotation processing would be quite reasonable for a job ad seeking to hire someone to do Java development

This goes back to the days where job ads would request N years of X experience. The big takeaway from the last ~10 years is that this type of requirement is unnecessary. As an engineer who knows the fundamentals, it's relatively straightforward to pick up a new tech stack.

I wouldn't want to pass on someone who spent the last 5 years working in C because we have a java stack.