I tried creating a word list using a passage from the LXX and it gave me all the Hebrew lemmas. Is this a bug?
The Add to Word List only adds lemmas and not surface text.
The Septuagint with Logos Morphology only has Hebrew lemmas in its interlinear data. Its interlinear data is used for doing Greek/Hebrew comparisons. That must have been the one you used.
Try using the Lexham Greek-English Interlinear Septuagint instead. It has the Greek lemmas for each word.
P.S. Aren't word lists still in beta (or am I mistaken)? This should be discussed in the beta forum to avoid confusion.