It is pretty clear it is
Not many companies care about this and there's little enforcement so far, I think it's fair to think about this though if you're running a privacy-focused web service from Germany.
[1] https://edpb.europa.eu/sites/edpb/files/consultation/edpb_re...
Not customers data.
By the edge locations, I'd assume he's serving cached static files, such as his blog or tracking scripts from there using CloudFlare. Assuming CloudFlare is not falsely advertising their GDPR compliance, the author is also fine.
As far as I'm aware, there's no requirement imposed by GDPR requiring that data stay within the EU as long as you have DPA's with Cloudflare, AWS, and any other data processors.
DPAs are very easy to sign with AWS and Cloudflare.
I also don't understand your complaint about "200 edge locations". Are you expecting him not to use a CDN?