It’s a design defect in all Russian tanks.
They have an auto loader that is very fast but the ammo is exposed and up in the turret.
The auto-loader in the T-72 is relatively fast for the type, but a human loader slamming a one piece fixed cartridge into a semi-auto sliding main gun breech block is noticeably faster then the T-72 mechanical autoloader. The 125mm round used by the T-72 main gun utilizes a two part projectile, because the warhead and the propellant charge must be loaded into the breech in two separate stages due to the length of a fixed cartridge and the space limitations in the cramped T-72 turret.
So a well trained and strong human loader is quicker for that all important first or second engagement winning shot that usually determines who will be the victor in a tank vs tank shoot out.(At least until he gets tired.)