I'm pretty sure during an interview once someone made a very similar joke when I'd written using Rust syntax instead of Javascript. I thought it was funny and thanked them for tactfully pointing out my syntax errors and confirmed I had been writing Rust a lot recently.

The only other choices for the interviewer are to bluntly say "you missed using semicolons" or to not say anything and be left to wonder if the person knows how to really write in C. The author of this post seems to think even considering any other choice than the last is rude since "whiteboard code doesn't compile so semicolons are syntactic sugar".

But if it does matter, baking in some understanding of the charitable reasons why (that the interviewee is proficient at multiple languages, especially in the popular ones at Apple like Swift) is actually the nicest thing the interviewer could have done.

The post author seems to me hostile to being corrected. Given that every code review I've been in requires being corrected dozens of times about errors large and small, I wouldn't want to have to deal with their uncharitable attitude towards feedback from coworkers/collaborators.