Yes. Liquid and powdered pectins are different, chemically. The powdered versions are expected to interact with the sugars and acids in your foods, and are added prior to cooking. The liquids are added after cooking is done.

While I had hoped that one could just prepare a liquid from the powder, apparently that's no easy to do in a normal home kitchen, and all the stuff I can find on the subject tells me to just use what the recipe calls for.

Thankfully, I have found the stuff the recipe calls for, so it is full steam ahead!