Hi Morguse,
My very late answer- I wouldn't be surprised if you saw this as a cake ingredient. Because as Americans like "ready-to-bake" products, you can buy a cylinder of cinnamon rolls at the grocery store and open the package, put them in the oven and get "fresh-baked" cinnamon rolls. So the recipe you saw used these uncooked cinnamon rolls to make a coffee cake. You take the raw cinnamon rolls (dough) and squish them in a loaf pan to create a cake (possibly adding additional ingredients).
I typed "pillsbury cinnamon rolls" on Google IMAGES and saw perfect examples to see how these products are packaged in a cylinder. In French supermarkets, you can find similar packaging with ready-to-bake pain au chocolat, for example.