Item Cat NLN appears not relevant for picking even it is relevant in 0VLP

Dear Expert,

We have an issue in on the behavior of the item category we assigned to the replenishment delivery. The transaction starts from an STO-PO and create a replenishment delivery on the background via VL10B. The replenishment delivery was successfully created. The weird thing is, item cat NLN is relevant for picking. I checked the item cat assigned to the replenishment delivery and it shows NLN but it appears as not relevant for picking as picked quantity column is uneditable. Seems weird and this is my first time to encounter such issue. I tried browsing the net and had no luck to find same scenario. Can somebody please tell me what could be the possible cause of this issue? Thank you in advance!

Kind regards,

Mark