It's hard to tell without taking ukemi yourself or talking to people who have, or knowing the relationship between the uke and nage...
But it does rather seem as if he's cranking the pins hard once the ukes are fully controlled and have submitted. So I can see how someone could say it looked ugly. It looks like he's taking advantage of someone being trapped to hurt them further.
It could look that way yes. I can only talk from personal experience. We used to receive pins in such a manner and thus learned a very specific lesson. What could happen.
This rules out what I hear many talking about as to the effectiveness of pins for until they have them done in such a way they will always have a thought that they 'could have' escaped.
This I believe is what was being emphasized by Arikawa Sensei. It actually takes great control to do what he did and yet not injure the opponent.
Many nowadays would indeed say that is rough, I prefer 'old school' myself. However, if not learned as he showed then that is one more lesson lost. The uke learns how to cope with it is one major uke lesson, especially if they kept zanshin all the time like Niall did. The nage would have to be pretty experienced to do such comfortably and confidently, knowing exactly how far to go. It's a skill.
Such is my view.