I notice that the example 「外国語を学ぶのは、大変だがやりがいの存る事だ。」has blue around the expected 「学ぶの」but also the 「は」is this just a mistake or does the 「のは」 relate to a different usage of the grammar term?
I'm also wondering if there is a difference between these, aside from related specific grammar points like ことができる. It seems like, in general, の is far more common for simply nominalising nouns.
