It’s been a while since I did this lesson, but I think I remember also trying to use arrow function syntax for the callback function within the .forEach() iterator, just like you have. Again, I think it was marked as incorrect, when it clearly shouldn’t be.
I also remember having an initial empty arrow function marked as correct, only for it to trigger incorrect when the .forEach() iterator was added within it. And I’m pretty sure, just like you, I thought it was caused by using arrow function syntax within .forEach(), but in the end discovered that it was the previously accepted (then unaccepted) initial arrow function!!
My original post only included a small sample of the problems I encountered with this lesson…
If you feel inclined, and have the time, then I think it would be a good idea to send a bug report to @alexcraig, in the format he asks for here 
Seems like there are still issues with this lesson…