The silly thing about rugby refereeing is that they're so anal about the no arms / shoulder charge. It's almost like its a point of pride that differentiates them from rugby league (although RL has now also banned shoulder charges, but for decades that was a big difference between the sports). They've doubled down on this in the last few years by getting paranoid about any head contact.
So through referee goggles; Mako's act becomes a late shoulder charge to the head (albeit without much force).
In reality it's just a cheeky bump to the kicker.
If you're going to bump someone late and get away with it, you're obviously not going to use your arms. A late tackle gets seen, a late little 'subtle' shoulder to shoulder (viewed from the corner of your eyes) just looks like an accidental coming together. But if it does get seen then the punishement is often far out of context of the crime.
Rugby refereeing is currently silly because WR head office are removing the ref's room to use their common sense.