Wej not requiring a negative verb is very difficult for me.
Yes, Klingon is not a negative concord language.
Remember that wej is an adverbial, not a negative. It tells you something about how the verb is performed. In this case, we have a verb maSopchoHpu' we have begun to eat. In what manner have we begun to eat? Not yet.
Thank you. I'm so used to agglutinating languages being negative concord languages that I did not even think of it in those terms.