What about all of the people who bought pizzas and dish detergent (or whatever that deal was) for points, bought more, redeemed, bought more, redeemed, and so on. It's the same scenario. Did those people have all of their points taken away? If they didn't, it would be awfully hard for PC Plus to justify taking the soup points away when they didn't take away the points when people did the same thing with much more expensive items.
ETA:
I just went looking for the clarification on this, and they sure went out of their way to bury it in the Terms and Conditions at a link in tiny font at bottom right on the website. Comparatively, when you look through the Help Centre, where most people would look for information, there is no mention of not receiving points on items you pay for with a redemption. Nothing under the section you would expect to see it in. Sneaky.
How do I earn points?To earn points, just load your offers to your PC Plus™ card online or through the PC Plus™ app, then show your card when you buy the qualifying items in-store. You’ll also get bonus offers, flyer offers and in-store offers to enjoy. The more offers you take advantage of, the more points you earn.