My ShopRite in Hamilton did this about 6 weeks ago. They said ShopRite had lost more than $10M in product because people weren't scanning all their items.
You can still scan more than 20, but you certainly can't go thru the lane with a full shopping cart the way you used to.
My Shoprite never seems to have enough manned checkout lanes open and have over 20 self check out spots sonthere is generally no wait even with full cart self option. Interesting to see how this all works out.