Asked to remove breastfeeding cover during landing

I flew Alaska today with my 4 month old and started to nurse on the decent with my nursing cover. It’s very light and drapes around my neck. A flight attendant said “you can’t have that while landing.” I told her I was breastfeeding and she pointed “you can’t have that around your neck.”

My husband and I were genuinely confused, so they would prefer my breast be out while nursing? The nursing cover helps me make sure he’s latched while not having him smothered in clothing.

Can someone point me to a policy or reasoning behind this? I can wear a scarf and sweater but not a nursing cover?