They're serving the HTML, they have every ability to track individual web requests without modifying the content they're serving.

I understand how it technically could work. My response was more centric to the fact that CF has been doing this for a long time and you should probably know better when selecting a vendor / feature like this.

Again, this isn't anything new.

100% But this does not give you any useful personal data :)

Or data for the increasingly invasive Cloudflare captcha.