Here are my observations, for what they are worth:
I had to add water to the sauce--a scant cup.
The pasta took as long to cook as it would to boil water and cook the pasta.
I used tomato sauce
The sauce was smoother and better.
When I tested the pasta I kept thinking it was going to be ruined, but then it suddenly became perfectly al dente.
For the record, I was using 100% whole grain penne pasta.
So the next time you cook a marinara or other tomato-based sauce, if your pasta will fit in the pot, dump it right in. In my case, I had to up the pasta cooking time from eight minutes to fourteen minutes. You'll save washing an extra pot and colander, too!