The general way to handle this as an interviewer is really simple: acknowledge that the interviewee gave a good answer, but ask that for the purposes of evaluating their technical design skills that you'd like for them to design a new system/code a new implementation to solve this problem.
If the candidate isn't willing to suspend disbelief for the exercise, then you can consider that alongside all of the other signals your interviewer team gets about the candidate. I generally take it as a negative signal, not because I need conformance, but because I need someone who can work through honest technical disagreements.
As a candidate, what's worked for me before was to ask the interviewer if they'd prefer that I pretend ____ doesn't exist and come up with a new design, but it makes me question whether I want to join that team. IMO it's the systems design equivalent of the interviewer arguing with you about your valid algorithm because it's not the one the interviewer expects.
