Done and done. OD&D , B/X, and AD&D advancement is most quickly achieved by gaining treasure. To that end, engaging in the most combat possible does not equal the greatest treasure gain possible. Fighting everything then hoping there is treasure will more likely kill you than produce XP.
Finding out where the treasure is via exploration, then figuring out how to get it while expending the least amount of resources possible while avoiding conflict with broke monsters is the smartest path to the most XP.
In 3E onward "the encounter" became the basis for XP so more killing DID become the fastest way to gain levels. This was a major game changer and quite a few people noticed the shift in playstyle that resulted from this.
So saying EVERY edition was combat driven is simply incorrect.
You checked absolutely nothing.
I know how the game was played at conventions, general groups, and the like. They fought and took treasure. Parties were made up of very few classes that didn't have to fight and take treasure. Getting around encounters without fighting was not only impractical, but boring.
Done chatting with you. You obviously don't want to admit how the game was designed...and more important how it was played by 90% plus of groups. Since I'm going by experience playing with a lot of different people and playing through every designed module from one of the least combat focused like Tomb of Horrors or Slavelords to the most combat focused like Against the Giants or Keep on the Borderlands, I'll trust my view over your theory. I also played competitively a few times cons. Those games focused quite a bit on combat, though they did include more puzzles. Almost never did they include accumulating treasure absent combat.
D&D was designed to focus on combat because the most people have the most fun doing combat. Doesn't mean you can't do other things. The design of the game is built for killing and taking things. It is the paradigm of the system.
Everywhere I ever played, we spent well over 50%, probably nearer to 70 or 80%, of the time in combat. That means the other two "pillars" divided up what remained.