Good observation Matthew. Frequently officers will use a leg sweep technique or a single arm takedown (think variation of ikkyo) to move an offender to the ground. What happens too often is that they don't move with the suspect and find they are trying to hold the offender's weight against gravity. The result is the individual will end up face down with his arms underneath himself. That's where it starts to get interesting and dangerous to all. With the hands and arms uncontrolled, the suspect remains a threat and the officer(s) have to get the arms freed and then secured. In most cases that when you see officers pulling on the arms and giving distraction blows. Once the arms are freed and handcuffs applied, the best practice is to roll the individual over to his back, sit him up, and while supporting his upper body, allow him to get his own feet under himself and stand up to be moved under his own power.
Something I have observed when watching "COPS" or other, is the officers have the offender in a position that will 'cause' them to struggle, and be yelling 'stop resisting.' I know that there are certain pins - applied a certain way that I am going to move, even if my mind says comply.
I don't know if it's the adrenaline of the situation, or they just don't recognize it, On the other hand while backing off slightly just might make it easier to comply, it also might give the offender another opportunity. I don't have the answer - just one of those things I think when I watch some of the takedowns...