This is where I get lost, Smithies does 2 head shots on Huddersfield, no sin bin, no sending off, they lose their best chance of a trophy in years,

Wigan’s next 4 opponents now benefit more than Huddersfield.
How can this be right?

the Yates one getting a 2 game ban is a joke, nowhere near as bad as Smithies 2nd one

Not ideal but it's been like this for donkeys with judgements handed down post matches. I suppose refs will always miss stuff and the thinking must be that a belated ban is better than no ban at all.
As for Hudds, their own lack of attacking ambition in those last 15 mins did more to scupper their chances than any non-decision by Child IMO.

I agree about their lack of ambition but that May have worked v 12 men for 10, 20 minutes or rest of the match.
The danger with refs not wanting to sin bin or send off in big games is it encourages players to go after key playmakers to win the game and if ban comes post match, so be it.

Not only different opponents but also in a different competition.