To some extent I'd say it is indeed reasonable. I had observed the effect for a while: if I walked away from a session I noticed that my next prompt would chew up a bunch of context. And that led me to do some digging, at which point I discovered their prompt caching.

So while I'd agree with your sarcasm that expecting users to be experts of the system is a big ask, where I disagree with you is that users should be curious and actively attempting to understand how it works around them. Given that the tooling changes often, this is an endless job.