From an engineering feasibility/cost standpoint: there is no scenario in which they could log (as in packet capture) and dedupe all traffic without a nation-state-like (alphabet orgs, interested companies a la Google) budget.

CloudFlare's (non-enterprise) prices simply aren't even in the required order of magnitude.

Now: whether or not metadata, request bodies, etc. are logged, and to what scale, is another story/discussion of possibility.

At some small, targeted scale, it's safe to say that total duplication (certainly request bodies, etc.) is possible, if they were so interested.