Serious question: What does making an announcement while the market is closed actually do? Are you not just throwing money to the people willing to trade after hours?
people trading off market are taking their own risks willingly, the market itself tries to be fair w.r.t. reported
if you are listed, you effectively agree to release info on certain terms, so that off-market don't get a better advantage also
When I had posted this, there had been no tweet, just a leak from a CNBC reporter with three lines : breaking news, Jack is rumored to be leaving, stay tuned for more info.
there was a massive info asymmetry, so NYSE had to halt trading until it deems news has percolated enough, I guess.