I would expect a recruiter for one of the biggest tech companies in the world to have at least some basic understanding/idea of even what linux is - that's not a big ask at all.

Moreover, if I'm a recruiter, unless I'm a domain expert, looking to hire someone into the field and they say they already have it on their resume, I'm going to go and double check their resume and double check my own understanding before I go any further to avoid issues like this.

The only person who looks bad here is the recruiter, and it's entirely their own fault.