These lists are some of the clearest examples of the manpower shortages, likely the result of extreme corruption and graft, that Russia has been facing throughout the war. When a Motorized Rifle Squad (MRS) is budgeted for (and claims to have) 9 men, but the commander only assigns 6, he gets to pocket a fair chunk of change.
So, when you deploy with 6 men instead of 9, how do you manage this most basic maneuver? You need 2 in the BMP, so those are locked in. Do you leave one poor schmuck to try to defend the BMP all on his own, while a full maneuver team moves on the enemy? You aren't going to get very good covering fire that way.
It may not seem like a huge deal, but the number of troops in an MRS has a very clear lower limit before it suffers a significant loss of combat effectiveness. Take, for example, a standard MRS maneuver to engage and destroy an enemy squad. The MRS is divided into 3 parts: 2 men in the BMP, 4 men supporting the BMP, and 3 men maneuvering to destroy the enemy.