I have no doubt that this guy is scummy, but this is a total nothingburger. He sold, for him, a tiny number of shares on a day where the stock was slightly above where it had been averaging, but even right now it’s still up for the month. Moreover, the expectation of every executive at Unity must naturally be that they expect to make more money with this new plan. Some developers and gamers may be mad, but Wall Street should be happy and the stock price should go up.
Phrased another way: he sold stock a few days before announcing a plan to increase company profits.
Typically there's some kind of plan where they have to announce sale of shares well in advance or a 'trading window' when they can buy/sell shares freely.
Insinuations of insider trading are going off too little info so far. That said it's not a good look for any of those people and I'd guess the FTC will investigate them.