The river was definitely obscure, but I don't think the noodle is at all. It is sold in virtually every US grocery store and is a favorite among college students because it is dirt cheap and takes a minute to prepare.
For some reason, I didn't get the "literally 8" clue until I read your post. I didn't like that - you could say that the ph "count" of the puzzle is literally 8, but I don't see how the ph level of the puzzle is literally 8. Level is not a synonym for count even, as far as I know, for any obscure definition.
One of the merits of the puzzle, IMO, was that the second ph in each word was followed by a different letter. I thought there would be a lot of phy endings, once I got the theme, but there was nice variety.