It's important to remember when calling HCT, that the runner does not have to be pulled "backward" although this is usually the net effect. The runner must be pulled down immediately.
I have not seen either play in question but if the ball carrier in the above plays was grabbed inside the collar of the shoulder pads from the back/side, it is possible to have a HCT if he is pulled immediately down regardless of which way he falls.
In the UCLA game, it is possible to be dragged along as long as the "pulling down" portion of the play by the collar is immediate based on interpretations of the philosophy that I have heard. Additionally, if a runner is strong enough to overcome the pulling down portion, it is still a foul if he remains upright.
Thoughts?