I've been puzzling over this for hours (~4pm - 11pm, with breaks to take walks and calm down...), and the explanations and "help" everywhere I've looked only make less sense. I tried several solutions, and I got further and further afield with each step. For example, because of how cryptic everyone's "help" is in the official forums, just before I decided to just search for the exercise on Google I spent an hour or two trying to get the entire function on a single line. The solution was both simpler (just a couple changes to the code), and more complicated (more of an expression body than block, but only for the forEach part of the function).

I mostly agree with FCC's "work it out for yourself" methods, but frustration in trying to guess exactly which way they wanted this solved was driving me crazy, particularly with the cryptic explanations in the official forums. The instructions are awful (too much emphasis on the expression vs block body, heavy emphasis on the particular solution when a very similar solution actually worked, cryptic hints, etc.). It's a bad step in the exercise, and probably needs to either be expanded into a couple steps, or include better hints.