Yes, I've had similar thoughts. I think when successfully "understanding", people see something in multiple different ways, ask Why? a lot, then finally relax once they're sufficiently convinced. This may use different kinds of cognition, like visual, kinesthetic, etc. And it may feel like diverse parts of their mind are at various states of being convinced/unsatisfied.

Whereas, when trying to "memorize" something, many people just kinda... hope the thing stays in memory through some unknown process. But you can "cheat" by consciously leveraging various cognitive abilities. (http://en.wikipedia.org/wiki/Method_of_loci#Contemporary_usa...) (Along with various little tips, like use lurid imagery, it's probably better to visualize large spaces you can walk through rather than tiny ones, etc.)