Ok, it finally kicked in and I’ve now disabled it.
What it did was replace our Moderate cancellation policy with a Non-refundable policy and knocked 10% off the prices. That’s it. I tried a selection of dates (using Epic privacy browser) and it appears that the Non-refundable rate appeared 6-8 weeks before the booking date, further ahead than that, our Moderate policy applied with no option to book any other way.
No notification to potential guests that they were making a saving and, more importantly, no way for the guest to make a choice between Moderate and Non-refundable.
Oh well, it sounded like a good idea - actually it is a good idea, just a pity about the front end implementation, or rather lack of implementation!