But the situation has changed now!! Now it has basically turned into trench warfare with modern weaponry combined with urban warfare with the presence of noncombatants, so of course, the rate of advancement will be slower, and then you take the muddy terrain into consideration, and it all begins to make sense.I don't remember this in theory. But I remember about deep coverage by motorized columns. And the Russians did it. Look at the initial period of the war. Even this operation had to be on a large scale.
Plus, them Russians have a manpower shortage, so they can't really afford to be reckless while planning an assault.