There's a distance from knowing Python enough to find your way around in projects to knowing it enough to solve coding riddles. The latter requires the level of familiarity attained only with regular use. Plenty developers go by their daily jobs without having to write a single line of Python.
I'd actually say it's the former that requires familiarity with the language. The latter only requires you to know some basic looping/control constructs. You don't need to know anything about classes or modules, for example. No need to understand async vs threads vs multiprocessing.
Honestly if you write psuedocode for an algorithm, there's a decent chance it'll be correct Python even if you've never seen Python.
