Well I know that now because I watched a bunch of prep videos and then easily passed interviews despite my experience not significantly changing in the intervening time. But that's my point; if you don't prep you have to just guess which aspects of this pretend scenario you're meant to be taking seriously and which are OK to gloss over. I had other interviews go off the rails because I offered too much detail about a smaller part of the system and discussion of it dominated the entire time but even though the interview kept engaging this discussion it wasn't actually what they wanted. "Don't bother prepping because you can't; it's just measuring your real abilities" is just not right, in my opinion.