The limits aren't exactly hidden in the ToS, the author just wasn't aware of them. If you don't pay money for a service what kind of support can you expect on a holiday?
Not only are they not hidden, they should really be common sense. That he seems surprised that Cloudflare doesn't cache 14GB files is surprising. There is some common belief that every service has infinite capacity in every dimension.
And the price for what he did would have been extreme. Serving a 14GB is something like $1.19 USD on CloudFront.
It sounds like he was operating in tiny land and expected bills to be commensurate, so it just seems irrational to expect a low or free tier of another service to do this for nothing.