I took this as meaning that it should be obvious from the layout that it was a LaTeX document, but I agree, this is not something that i've ever considered when filtering CVs.
As a proficient LaTeX user, this is the stupidest take I ever saw on resume tips. I mean, your skills and experience do not vary with the document system you used to generate your CV. Some hiring managers swear by MS Word templates, other hiring managers ask for Europass, others ask you to fill in a form and request a cover letter. It would be stupid to assess the suitability of any candidate on this sort of bullshit.
To me this feels like a case of a publisher passing on a novel because the author wrote it using notepad.exe versus vim.