OTOH, it's a mentality which demands respect for any gun, regardless of its believed condition of loadedness or unloadedness.
Suppose you were to ask whether my XX-XX (rifle) is, right this instant, loaded or not. Fact of the matter is, I DON'T KNOW. It's probably locked in the safe (that's what I remember last doing with it) and its chamber is probably clear (I remember doing that before I locked the safe). If I need to use it, I will be sure to grab some appropriate ammo along with the rifle itself. BUT, when I open the safe and take it out, I will "assume" that it is loaded and check to be sure.
Because all guns are always loaded.
It's not just a rule, it's a way of life.
We are in violent agreement that all guns should be treated as loaded until proven otherwise (dry fire, disassembly, repair, storage, cleaning etc.) but if you don't acknowledge that guns can in fact be unloaded, the aforementioned activities become difficult.
I don't have an issue with the Gunsite rules, but for most people the NRA rules require less clarification.