So, in reality, the extra privacy gained from not doing ECS is hardly something with a measurable effect, because this information HAS to leak in any case. Even if make DNS encrypted, even if you employ encrypting TLSv1.3 SNI, the IP addresses will still leak, and with a much higher precision anyways. So, this we-don't-do-ECS-because-privacy is a rather pointless statement in the end.
The main reason that Cloudflare wouldn't share this info is to prevent competitors like Akamai to operate a CDN as good as them. It looks more like sabotaging competition than increasing privacy.
Exactly. Their own answers in the threads over here at HN are basically admitting as much — they claim to be working on solutions alternative to ECS, because Google and some others have more PoPs than Cloudflare does. They're obviously using this as a competitive advantage to slow down competing CDNs. And noone's talking about!