Peer review isn’t the issue here. His comments are about Arxiv, which is a preprint server. Essentially anyone can publish a preprint. There’s no peer or other review involved.
You are right that arxiv is an invite-only website, but once you are in, there is no peer review of any form.
It's very easy to get in. It's becoming a common target for grifters who will "publish" papers on arXiv because it looks formal to those who don't know any better.