This is an excellent question, and it gets to the heart of the matter about what scientific papers can actually tell you. Bottom line: scientific experiments intended for publication in peer-review never actually optimize any sort of protocol. To get published in peer-review, a medical research paper needs to show statistical significance (P<= 0.05), and the experiment needs to be as clean, simple, and unconfounded as possible. This is why you never see much in the medical scientific literature aside from “A versus B experiments”.
This is what researchers need to do to get consistently published and funded, but it does NOT result in the best or most useful type of information. But most people, including scientists, have come to believe that when something is published, it is the “optimal” answer. This is so rarely the case that I will go on record to assert that it is never the case.
The rest of the arguments get long, tiresome, and very statistical, but basically, to publish a study you need to pick one, clean, uncluttered variable. So, just as a “best guess”, we picked 5 pps for that study. It is not magical, it is not even a very good Idea IMO to use one pulse rate (because of habituation), but we needed to do this, because if we tried to publish any pattern more complex than that, the immediate reaction from reviewers would be that we “need to zero in on the one key frequency” (even though there is no such thing), and the addition of anything else adds confusion about what is doing what.
This is just the tip of the iceberg about why the peer-reviewed medical literature has become so utterly unreliable and impractical.
The bottom line answer for you is this: 5 pps is nothing magical for brain health. It is just a best guess, simple, monotonic (one frequency) value that we figured was in about the right range, and that would be publishable with less argument than a better pulse pattern that was more complex and variable. In a word, 5 pps is an experimental expedient, not a magic number.
My opinion: for brain health I would use any of the brain wave protocols on the M1 that I found agreeable… I use Alpha Wave myself, for example,