My understanding of the point of the story is that the bishops erred in stripping St Nicholas of his rank, and were then divinely convinced of the righteousness of his indignation against Arius.
In hindsight, we can appreciate that. But why should the bishops have trusted a vision if, as a general principle, visions and dreams are not to be considered automatically trustworthy? If some visions can be depicted based on their "good fruit", I don't see why lesser known visions with lesser known "good fruit" should not be depicted.
In hindsight, I think the iconographic portrayal of a vision of our Lady communing monks, originally revealed to an erring monk, has not led to anyone seriously believing that she is a cleric, or that women can be "extraordinary ministers of Holy Communion", or what have you. But the vision did lead to at least one man's repentance and the edification of others.
And all of that is beside the point that I could probably develop a theological argument for why it is not inappropriate to depict our Lady distributing Communion, even if it does not necessarily require the affirmation of women's ordination or any similar issues. It would be a bit of a stretch, but nevertheless a basically sound argument. I think quite a few "givens" in our tradition probably started out that way.