The SEC has very specific rules and even specific form [1] they must file when companies release information like this.

[1] https://www.sec.gov/forms

So if the founder goes on TV and announces their merger then it’s nonpublic information until they file the form? Everyone who trades on that is insider trading? That can’t be right.

Right but - that means the company employee gets in trouble for making the information public (via announcing it in public at the bus stop) - not that I would get in trouble for hearing it and acting on it, right?

Those rules regulate the company, not random people at a bus stop.