I suspect that depends on your perception of Nysalor. The Pelorians would say that he was a "great friend" and their memories of those times are good. It also depends on whether you believe Arkat and don't think that he was the Deceiver to begin with.
It depends on your perspective. Arkat became known as Gbaji at the end of the wars and was also seen to be a "deceiver" by many who followed him and then left after he changed cults or species.
I think it is a label that one side uses to tarnish the other
Glorantha abounds with writing that is from a particular perspective and opposes material written elsewhere. The Arkat/Nysalor debate is the best example of that and it speaks to, I guess, a deep fascination that Greg had with myth being one form of propaganda.