I think it depends on who gets to choose the programming language.
If you're interviewing for specific language skills, then what you say is clearly true.
If it's a general coding skills interview, I invite the candidate to code in whatever language they like. More often than not they choose a language I am sufficiently fluent in to follow along. In rare cases I need to ask them to explain a thing or two. In very rare (but generally quite fun) cases they choose a language I am totally unfamiliar with; this tends to lead to interesting discussions.
In all of those cases the full coding transcript is captured and, if necessary, can later be additionally reviewed by/with someone who knows the language well.
P.S. Also, their thought process and approach to problem solving is just as important as the code, and is largely independent of the choice of programming language.
If you're interviewing for specific language skills, then what you say is clearly true.
If it's a general coding skills interview, I invite the candidate to code in whatever language they like. More often than not they choose a language I am sufficiently fluent in to follow along. In rare cases I need to ask them to explain a thing or two. In very rare (but generally quite fun) cases they choose a language I am totally unfamiliar with; this tends to lead to interesting discussions.
In all of those cases the full coding transcript is captured and, if necessary, can later be additionally reviewed by/with someone who knows the language well.
P.S. Also, their thought process and approach to problem solving is just as important as the code, and is largely independent of the choice of programming language.