You are right. The distinction "for no reason" makes a difference, but I suspect there was a reason of which the OP might not yet be aware. I think, currently, there is no APPARENT reason.
There are some funky intersections out there. I once made a left turn at an intersection that was kind of H shaped in downtown Fort Lauderdale, FL. In the middle of the turn, I looked up, saw a red light, and stopped, wondering if the light I was looking at applied to me. I was rear ended. From the other driver's perspective, there was no reason for me to stop, but I think my reason was pretty good.
One time, I was making a right turn on red. After I started pulling out, I saw a car that was about to make a U turn in front of me. Since the car making a U turn had the right of way, I stopped to yield to him and was rear ended. That particular driver was gabbing on her cell phone when she rear ended me, but I wonder if she considers my reason for stopping in the intersection valid. Actually, I don't much care what she thought. Both of these careless drivers were cited for rear ending me, so I guess the officers thought my reasons for stopping were pretty good.
My point is that it doesn't really matter whether this driver we are discussing had a reason. For whatever reason, he didn't want to proceed through the intersection. Maybe he saw a dog he thought might run out into the street. Maybe there was a mechanical issue. Whatever his reason for stopping, there is no excuse for following too closely. Whether the car in front of you is passing through an intersection or not, every driver should leave enough following distance to be safe.