This assumes that someone, for some reason, has created an easy and instinctive to use magical system for everyone in the world.
Not really, it just assumes someone can teach you the ropes~
Again, if someone knows how to do magic with IFs and ROUND, then they'll teach their disciples how to do magic with IFs and ROUND.
If one of those disciples discovers CEILING and FLOOR, then they will have obtained knowledge beyond the reach of their master, and they might teach their future disciples that too... Or they might keep it to themselves and only teach IF and ROUND to their disciples too, who knows?
As long as you know how to manipulate it, you don't need to know the intricacies behind it. Maybe the person that discovered the FLOOR function of magic did so by diving deep down into the origins of the ROUND power and understanding it to its utmost... But they don't need to show their decades of research to their students in order to teach them how to use this part of the magical power~
It doesn't need to be standartized nor does it need to be widespread, as long as somebody teaches you the how, you can make do without knowing the what~
... Not to mention people that naturally manifest magic by instinct and stuff, those definitely are clueless about the what, but they know that if they think hard and try doing a poof, it will release a fireball~