Earlier quoted context omitted.
I don't think you can really learn C in a weekend. Not with all the ins and outs of undefined behavior. And if you don't know your way around the undefined behavior in C, you're going to make dangerous mistakes.
For various meanings of 'learn'. My point is that you can be writing useful programs in c in a weekend. Obviously said person would not be an expert, but I've watched competent programmers try to learn complex languages like Haskell and Scala; there is a far more complex mental model that one needs to build before they can use those languages specifically because of all the automagic that happens in the background.
We'll need to define criteria for "useful program" but I believe most people could write useful programs in most languages in a weekend.
> I've watched competent programmers try to learn complex languages like Haskell and Scala
> far more complex mental model
I think its more that those languages are different, not that they require a more complex mental model.