I agree. Poole didn't expect to get punched, but that doesn't meet the definition of sucker punch in my opinion. To me a sucker punch is when someone gets completely snuck or gets punched by someone acting as if everything is cool to get close enough to punch the other person.
Will sucker punched (slapped) Chris at the Oscars because seconds before walking on stage, Will was laughing at the joke Chris made about Jada. Therefore, I can understand why Chris didn't think Will was coming on stage to hit him. Had Will yelled, "Keep my wife's name out of your fucking mouth!" prior to walking on stage and hitting Chris, it wouldn't have been a sucker punch (slap).
Once Green approached Poole in an aggressive manner, Poole should have been on high alert. That no way excuses Green, and Green was definitely wrong. However, I don't feel it meets the definition of a "sucker punch".