My position is Shaw knew about Garithos and spat on his grave, while Kristoff reminisced about the time spent with him. Garithos doesn’t come in 15+ years of Alliance questing.
Anything else would be you filling plot holes. The very same thing you’re accusing others of.
The Alliance didn’t care about Garithos enough to seek revenge or anything. But that doesn’t mean the Alliance is required to entertain any emissary from a faction that literally just stabbed them in the back.
I care less about Garithos and more about the actions of the Forsaken. One of the most consistent ways that people try to cover for the Forsaken’s actions in this scenario is to try and make it about Garithos and how terrible he was and how if you don’t think the Forsaken’s actions were good and justified you must love Garithos.