Only in insanityville is the Lumia naming scheme the main reason for WP's low market share. On the other hand, they are correct that it really is absolutely and truly awful. It's inconsistent and for most people utterly incomprehensible, not to mention unmemorable.
I could list a lot more goofs and inconsistencies than the article did, but the 640 XL is at least a very good step in the right direction. It expresses the relationship to the 640 (same hardware) and everyone understands the meaning of XL (just bigger).
I hope MS takes this even further and cleans up the current mess.