I think the ref got it absolutely right.
Too many times this kicking the ball from a scoring players hands is ignored.
The YC was harsh, but mandated when there is a PT (that's the Law that should change, ref should have discretion to not give YC in unusual circumstances, like this)
The YC is NOT mandated. The ref does have discretion.
[LAWS]Ruling in Law by the Designated Members of the Rugby Committee
Law 10.2(a) is Unfair Play relating to Intentional Offending.
The two paragraphs in Law 10.2(a) must be read in conjunction, having due regard to the heading 'Intentionally Offending'.
Therefore, if a penalty try is awarded as the result of a player intentionally offending, then the player must be either be cautioned and temporarily suspended or sent off.
Examples of this would be after penalty tries resulting from:
• a collapsed scrum
• a collapsed maul
• a defending player intentionally offside
• a defending player intentionally knocking down the ball.
If a penalty try is awarded as the result of a player unintentionally offending, the player, as well as being liable to cautioning and temporary suspension or send off, can be admonished by the referee.
Examples of this may be after penalty tries resulting from:
• mistimed tackle (early or late, but not dangerous)
• unintentional reactionary high tackle, but not dangerous.[/LAWS]