DonAndres
Wild Man of Borneo
But the tackler's strength equally affects perception, if a strong player commits to a tackle it could be completely clean and someone would still be sent flying, it's not a PK but it looks like it just like you pointed out with the Neymar vs. Rooney example. Something similar to the incident just happened, Sagna and Rooney were both racing for the ball and both tried to shove each other out of the way, Sagna stumbled and conceded a throw-in but it wasn't a foul, Rooney was just stronger.
Sprinting in and colliding with Rooney isn't the same as two players grappling and shoving each other out of the way. What Giroud did cannot be deemed as a clean challenge.