Not bash the researchers or the quality of their research but I'm unsure if a negative result would have been acceptable to their continued funding. I'm sure P&G would like to use this research to sell their diffusers after all.
Usually if the results are positive they're not exactly made up. Negative results just don't get reported. You should always maintain skepticism though and be critical. Those are still good qualities and I don't want to discourage that in any way.
(Sorry, little ranty below)
I say "not exactly" because every researcher does embellish their work a bit. I'm not going to directly criticize the researchers here (well I will) because this is more a product of the reviewing process (i.e. researchers) who are often quick to reject. The bigger issue is that reviewers see themselves as filters (i.e. adversarial to the reviewed work) and not as editors or consultants (i.e. on the same team as the reviewed work). I'm not sure if this is a psychological thing or incentive (both for sure) but it's probably something we should be discussing due to the feedback loop that it creates and is resulting in more a prolific environment where it is impossible to distinguish an ad from science. Which isn't good for science and especially for people trying to read science (i.e. why science communicators are often shit).
I'm also a big believer that we should be publishing negative results. Fuck man, most research is failing. You find out how to do something by failing to do it a hundred/thousand different ways. Why aren't we encouraging this? I thought papers were just about us scientists communicating with one another...
This is where conspiracy theories are born, and why they are so hard to fight.