An update on this and a bit of a warning:
Of the ten I bought on Wednesday, eight had the new tab & warning on the back that the checkout operator has to remove to access the bar code. Two were of the old style where the bar code was visible through a cut out portion of the cardboard.
This morning I purchased ten (in two lots of five) and all were the old style with the bar code already exposed. For both transaction the 5000 bonus points appears on the bottom of the docket (though yet to hit my account).
So beware the new style cards and perhaps keep it to five cards per transaction.
