Watching the play, it looks more like a missed interference call than anything. The Pittsburgh defender definitely made an effort to hold up Bunting, who was in pursuit of the puck. Nobody has ever accused the Department of Player Safety of being consistent or fair, so it's not a shock that we see yet another confusing ruling coming down from George Parros.
What is very confusing is the timing. That game was played a week ago. Why would the NHL wait this long to announce the fine? The 5-second clip posted alongside the announcement offers no explanation beyond what the release said. It's extremely odd that a fine would come now and not within a day or two of the incident.