My Walmart purchase two days ago also got only 1x. It was coded as grocery. It is only a few dollars worth.
I don't know the true answer, but I suspect not all the registers at Walmart are coded the same. I noticed that a couple of months ago when I got my new CSP and it offered $50 grocery credit. One of my Walmart purchase was coded as grocery and I received the grocery credit. Another purchase I made later on the same day at the same Walmart was coded something else (I forgot what the category was) and I did not receive the grocery credit.
FWIW, this happened at one of the Walmart "Supercenters", and I used different self check out registers.