Doing each test eight times surprises me. Once the drivetrain is warmed up it should take no more than three to get two identical graphs. I suspect their double roller dyno was raising the tire temperature and therefore pressure resulting in lower rolling resistance as they kept doing runs.
No doubt the tuneup helped some but what they did was a simple A-B test. Of course you couldn't do it with the injector cleaner but the real proof is in an A-B-A test where you run a third test by putting the old parts back on the engine to verify that the power goes back down to the original numbers. But nobody (but me) even thinks of that after they get the results they were after.