How did they come to that conclusion? Of course the creators of the idea would support the idea... and of course you could take anyone and assign them a best-fit within any parameters you've chosen to set to represent a "fundamental personality".
Basically you are insecure about not having a radically different personality in the scope of of all of mankind, or something. Perhaps it also bums you out that all people are approx. the same. Of course there will be a max level of variation that healthy humans are going to be programmed to be able to cover, but within that, there is still variation from person to person. ALL OF LIFE is endlessly repeating patterns and cliches. Look at DNA. Look at all the other plants and animals and the behaviours they've kept ingrained in their nature from the beginning of time. There is a lot of repetition in life, but it doesn't mean life is meaningless or that you have to focus on the boring or repetitive aspects of yourself or others which bum you out.