This is the only thread I can find about the Chase Shopping Portal. I've just recently become aware of this, despite having a CSR for five years.
There are some pretty extraordinary bonus offers there. Currently Grubhub is 10 pts/$ on my Freedom Flex, and 7 pts on CSR. Today I tried it out using Grubhub, but paying with my Amex in order to see if I can double dip. There is nothing in the T/C that I can find that says you must use your Chase card to pay. Stay tuned.