As long as all the parameters were constant except for the manifolds, those tests provide a good comparative metric for manifolds. Do they show the true performance? No. Do they provide metrics that you can use to compare the flow characteristics of the manifolds in question? Yes.
That's certainly better than nothing. The test design should be refactored, we can agree on that, but the data from the test does provide conclusive comparison results that are valuable when making a purchase decision.