Just got a letter that offers 10,000 Membership Rewards points for enrolling in the Extended Payment option. It appears that if you have this option all purchases over $100 automatically go into the Extended Payment category and you pay 19.24%. I called in and got some confusing responses to my questions regarding how this works if you have Autopay the full statement balance. I was told that the point will be awarded 2-6 weeks after enrollment and would not be clawed back if you cancel.
Be clear I am not suggesting that anybody sign up to use this feature to pay off the balance over time at this rate. However it appears that you can sign up and override the 'Extended Payment' option for one or two cucles until you get your points - then cancel. I suggest further research to make sure. It appears that an invitation is needed to join.