Hmm. Glancing through this, it seems to me that it fails to distinguish between regional terminology (e.g., apparently in New Orleans they call cottage cheese "cream cheese"; some places the thing you drink water out of on a playground or in school is called a "water fountain" and some places it's called a "bubbler") and items that only exist in a particular region (e.g., there's only one word, albeit with alternate spellings, for "lutefisk", it's just that lutefisk is generally only made in the Upper Midwest; an "egg cream" is a drink that's not widely known outside the NYC area, as far as I'm aware, but it's not that it's known by different names elsewhere, it's just not made elsewhere). Those, two me, are separate things, and this dictionary appears to consider them to be the same.
Also, egg creams are tasty.