It wouldn't have been considered an assault at the time. Greta said the kiss was nonconsensual but she didn't say she was assaulted. She didn't press charges. For all we know, she enjoyed the moment. Why don't we stop getting offended on behalf of other people?
She doesn't look like she is enjoying it in the photo.
But that isn't the point - all sorts of things are captured in photos in the context of their time and place. And they become a historical record, even if the events they capture aren't something we'd approve of now, albeit accepted at the time. But we aren't discussing the photo and the real event - we are discussing the decision in recent times, with our current views on acceptability, to recreate that event in a sculpture. And that sculpture detaches the event from its context - no longer can you see all the other people round and about celebrating in Time Square. All that is left is a man aggressively kissing a woman who is entirely passive in her demeanour (not how she would be if she was actively enjoying it).
And then the sculpture of a man imposing himself on a woman is called 'Unconditional surrender'. The original photo wasn't called that - it was termed VJ Day in Time Square. The change of name seems to me to talk about the unequal nature of the interaction between the two people, not the war, as the context is entirely lost in the sculpture - that's what I find rather disturbing about the sculpture.