I don't agree with this at all.
The rules of music are built into human nature and have merely been discovered by musicians.
Is the rule that you double the frequency of a note for every octave something that was invented by musicians? No - of course not.
Is it a coincidence that all the different developing musics around the world through history have discovered many of the same rules?
No. The rules are there to begin with - we just find them, as physicists find other rules of nature. A major chord is always 'happier' than a minor chord - no matter who you speak to. It's a natural rule rather than a cultural one.
I think often it is the word 'rule' that is problematic here.
These 'rules' of music should be viewed as rules of nature, like gravity or natural selection - not rules to be followed, like not writing on the board in school.
I notice you prefer the word 'facts' - you describe a the rule of the triad using this word. You are simply substituting one word for another here though, due to a mis-interpretation of the word 'rule' in this context. Semantically I could replace the word 'fact' with the word 'rule' in your sentence with no problem at all.
There are no "rules to be followed" in music - you can do what you like. The natural rules of music tell you what the music you are creating might sound like (if, like many earlier composers, you write it down before you ever hear it) and what effect it may have on the listener. They also give you options to consider composing.
It's more (although certainly not exactly) like using the rules of physics to build a beautiful machine that does what it was designed to do, rather than slavishly following rules that must be obeyed no matter what. I don't think any composer in history has ever done that, or ever will.
Of course there are many cultural quirks on top - but these also follow the natural rules of music. By definition of the rules of music they have to! I may chose to spin an apple sideways as it falls - but it is still following the rules of physics.
And finally - the word rule at the free dictionary:
http://www.thefreedictionary.com/dict.asp?Word=rule
You are interpreting the word rule in context 2a:
"An authoritative, prescribed direction for conduct, especially one of the regulations governing procedure in a legislative body or a regulation observed by the players in a game, sport, or contest."
Clearly, when discussing music we should use the word rule in a different context - further down the page you will find it in the Thesaurus section as:
"rule - a rule or law concerning a natural phenomenon or the function of a complex system; "the principle of the conservation of mass"; "the principle of jet propulsion"; "the right-hand rule for inductive fields""