my experience, just now (typing at the pump):

brand new shell station (with seasons convenience store) on route 1 south in westwood (perhaps the newness of the pump POS is a variable; this was the large color screen that plays GSTV while you're pumping). my fuel rewards discount was showing $7.05. i manually entered my fuel rewards phone number, and got $1.55 off. i then entered my stop and shop number, and only got $1.50 off.

so perhaps a minor takeaway, at least for the new pumps, is to use your FR number for the extra 5 cents.