Armament haki is not the amp y'all pretend it is
Fans have a bad habit of DBZify-ing every other series, especially the big 3.
People seem to have this fundamental belief that basic armament haki functions like ki in dragon ball or Tsunade's strength of a hundred jutsu, where it basically just acts like a raw strength buff.
We know there's a difference between raw strength and haki because Garp told Aokiji to not use haki when training his strength. Training raw strength and training haki are 2 seperate things.
Zoro notes armament haki hardening/coating for its hardness and weight. The significance for this, especially for a swordsman, is that the finer quality of blade and more durable it is, the more the swordsman can use their full strength without the blade breaking.
This is basically the same as wearing brass knuckles. The increased weight add a little extra power to your punch, but the hardness and protection of your hands makes the enemy take more damage than just the raw power of your punches and you'd be much more willing to punch harder.
Basic armament haki is basically a brass knuckles level amp. People attribute too much to haki too often.