I would generally avoid any course that advertises itself as being designed to “set it apart from every other Japanese course” to justify charging you a steep premium. There’s good and bad Japanese learning material out there, like there is for most languages, but it’s highly unlikely that literally all of it (mostly developed by studied linguists as well as certified teachers with ample experience who are often native speakers) is ineffective, inefficient, or bad, which the author effectively suggests.
Learning a language takes time and effort. There are techniques, tools, and methods that will make it easier of course, and some will work well for you and others not so much. Anyone that promises you a be-all-end-all solution to the painstaking process of acquiring a new language, however, is doing so solely for commercial gain.
And while I admit that this is also a personal pet peeve of mine, it’s usually a giveaway when a language learning website or tool references Krashen’s input theory from the 1970s as “the science” when second language acquisition research has done so much more in the 40 years or so that followed.
Lastly, just because someone can speak an impressive amount of languages doesn’t mean they will automatically be a good teacher. There are fantastic language teachers that are nowhere near being polyglots and polyglots who don’t know how to teach.