Checks his run? Is that a second gif?
Asks Nige said, he commits to the tackle before the ball has gone (watch his head) and the whiplash is due to the physical mismatch not dirty play. It’s not tag rugby and these guys are not U9.
Watching the way these guys take the bit and then watching the L v MU match, at least #10 didn’t spent 2 minutes rolling around despite the fact that that must have hurt.
Edit: from JIm Greenwood Total Rugby and how to tackle: “a potential tackler running flat out is too easily beaten….you go to meet him, lower your centre of gravity, get your head to one side, and focus on driving your tackling shoulder up into his solar plexus. Your arms close round him, but the power of the tackle comes from checking his upper body, and simultaneously, as your legs straighten lifting his feet off the ground. You then drive through to put him over backward.”
This is how to tackle head on, so Lawes is not facing #10 head on and hence is not hitting the solar plexus, but everything else close to the manual…