It's only a problem if the candidate in the candidate-employee pair produce code that ends up in master and that candidate doesn't get hired.

My assumption would be that if a candidate's code is good enough to get released, then the candidate is, by definition, good enough for the company.

I also assume that most of the time spent in this "interview" in a live codebase is the employee asking about how the candidate thinks and decides on things, not for the pair to actually produce working code.

I also assume that the code used within the codebase is non-business-critical stuff like an internal tool.