I would say pushing boundaries (and maybe to a lesser extent just pushing buttons) is categorically different than trolling.
Trollings sole purpose is the reaction, to rile people up. You dont have any intention behind your words besides that. Or heck maybe you even lie to do it. "What if I post pictures of sad looking polar bears to Greta Thunbergs twitter account? Wouldnt that make her mad!? hahaha!" Thats a troll - Nothing is gained, nothing is learned, nothing is advanced.
Pushing boundaries is something different. You can have intent, social movement, and a message with it. Star Trek pushed boundaries when they had an interracial kiss, it wasnt just for shock value or trolling white people. Ellen coming out on TV pushed boundaries without trolling people.
Boundaries are generally placed by people for the purpose of holding certain groups back, and they deserved to be pushed and in fact broken. Trolling does none of that. Trolling is putting a flaming bag of shit on someones porch and ding-dong-ditching just to watch them get their shoe dirty. If they are old, fall over, and break their hip when they do it thats all the more fun to the troll.
Pushing buttons... more on the trolling end of things, but probably done in a more playful way, maybe even to someone you know and hope to have a positive relationship with afterwards. But really its a more mild form of trolling
Was it illegal to do what they did to the guy? Thats the only reason Elon says he would ever take any content down from X