What ARM64 machines are you using and what are they used for? Last year you were announcing Gen 12 servers on AMD EPYC (https://blog.cloudflare.com/gen-12-servers/), but IIRC there weren’t any mentions of ARM64. But now it seems you’re running ARM64 in full production.
I seem to recall Cloudflare hosts their some of their non-edge compute on public clouds? Like control plane stuff. Could be that.
I'm not Cloudflare, I just read their blog too much. As they hint in the article when mentioning secure boot, they've been deploying Ampere in parallel to AMD for several years now. Purpose wise it seems to be Edge related for efficiency reasons, but maybe they use them for other things too. You can read some more here https://blog.cloudflare.com/designing-edge-servers-with-arm-... and here https://blog.cloudflare.com/arms-race-ampere-altra-takes-on-... along with the original evaluation of Qualcomm here https://blog.cloudflare.com/arm-takes-wing/