Earlier quoted context omitted.
It's worth remembering that that's one operating mode. There are others.
If they can cache it, they can read it.
The operating mode described by the comment to which I was responding, that of CloudFlare performing all steps of SSL termination, is one operating mode available. CloudFlare offers at least one other operating mode in which they are not responsible for all aspects of SSL termination. In particular, they offer an operating mode in which they do not hold private keys. This is referred to as "Keyless SSL". Thus the concern voiced by the comment to which I was responding, that of CloudFlare stripping SSL, is but one available option rather than the only available option.
Clearer?