The reasoning may not be about typos, but the egonomics are. Also, following the tradition of those other systems doesn't make it better for Nim users. The context matters a lot.

And why are case errors a big deal in case-sensitive languages if they cause "undefined" errors or, better yet, are caught by static analysis?

(To your point about Python, I still think semantic whitespace is insane -- invisible code, as you implied -- and is a major reason I avoid Python when possible.)