In golf, players get disqualified quite often for minor rules infractions. In So's case, he didn't just break the same rule three times, he defied the TD by continuing to break the rule even after he had been warned.
I'm not fond of Akobian "tattling" on So, but he really did bring this on himself.
If you are told not to do something, but then do it again, it may be that you forgot.
If you are told twice not to do something, yet do it again, it is open defiance of the rules, or a powerful compulsion or need to do so.
He did not follow the rules and had been given two warnings? If this is true, he had a reason to do what he did, knowing the consequences.
Something is very wrong.