I'm generally confused by how much "ATS-friendly" matters, or what that even means. On one side of the coin, it logically makes sense that ATS systems would help recruiters pare down the list. I'd assume there is some auto-rejection happening, but how sensitive is it (getting rid of clearly unqualified candidates vs. rejecting marginal candidates vs. actually qualified but still rejected due to not being ATS-friendly…
I suspect that quite a few ATS were struggling to parse the PDF.