Booking.com rewards cashback using with cashback websites

Hi,

I am looking at the Curve rewards tab for booking.com. It says it cannot be used in conjunction with any other promotions or offers, I assume this means voucher codes and does not include in-site offers or cashback websites like topcashback.com.

Can anyone confirm this? Has anyone tried this already? It would be pretty ridiculously good if it was the case.