I think Matthews was indeed trying to get himself to a position where he could have a shot at the ball.

watching second by second, multiple frames per second (with my handy pause button)

7:55 matthews begins to stop and start a comeback (longest comeback route I've seen if that's really what it is but whatever)
7:56 ball is well away at this point... hand/arm fighting begins. argument could be made DB is holding WRs right arm and/or jersey
7:57 looks like both see that the ball is on its way to them and both are fairly upright..
7:58 extremely obvious which one is leaning into the other at this point.. forget the arm/hand battles of the previous 2 seconds, but at this point isn't there "illegal contact" at a minimum?? (but with the ball in the air at this point, seems PI would be the call?) ... anyway, Matthews likely realizes he's about to be pushed out of bounds, reaches around -- whether to try stay in bounds and get at the ball, or to "sell" the PI, who knows..

8:04-5 also notice the DB has the WRs left arm locked with his own right arm.. how else does the WR try to loose himself from that grip besides "pulling" it out? (while being pushed onto his back imo)

oh well, what's done is done. We don't know what would have happened on the free play, but I would have at least like to see them get a shot at it, rather than the ref swallow his whistle.. but then again, I'm a Cougar fan.