I think the distinction is that Namor and the Cabal did not make it possible for the Incursions to be solved meaning if the 616 was destroyed or not had no impact on the Incursion problem as it is presented. The problem still could have been solved by the inhabitants of another universe.
What they did keeps the 616 involved. Which is not minor...especially for meta reasons and out continued enjoyment of this book...but saying that did more than that is attributing more in story importance to their actions.
I can see how some might dismiss that distinction, but I understand it.