I have no issue with the PT as it looked pretty deliberate to me and is a Law 10 breach, but YC seems harsh despite the law suggesting that it was required (my highlight below). TBH, I probably would not have issued a YC, but im sure my assessor would have had words about that. I don't think it was all that controversial.
[LAWS]10.2 Unfair play
(a) Intentionally Offending. A player must not intentionally infringe any Law of the Game, or play unfairly. The player who intentionally offends must be either admonished, or cautioned that a send off will result if the offence or a similar offence is committed, or sent off.
Sanction: Penalty kick
A penalty try must be awarded if the offence prevents a try that would probably otherwise have been scored. A player who prevents a try being scored through foul play must either be cautioned and temporarily suspended or sent off.
(b) Time-wasting. A player must not intentionally waste time.
Sanction: Free Kick
(c) Throwing into touch. A player must not intentionally knock, place, push or throw the ball with his arm or hand into touch, touch-in-goal, or over the dead ball line.
Sanction: Penalty kick on the 15-metre line if the offence is between the 15-metre line and the touchline, or, at the place of infringement if the offence occured elsewhere in the field of play, or, 5 metres from the goal line and at least 15 metres from the touchline if the infringement occured in in-goal.
A penalty try must be awarded if the offence prevents a try that would probably otherwise have been scored.
[/LAWS]
As for the Conrad Smith steal, it was a 50/50, as he may well have had possession before the original ball carrier went to ground / or knees touched the ground. When I paused it at that point I think the ref was blocked by other players so probably would not have had a clear view, so at that speed I think fair enough to play on (white had no support in coo-ee either).