So I keep seeing things like "insiders sold X amount at Y date, they must have known Z" but I thought that as an insider you can only sell a certain amount at certain times that are pre-defined before the true value of the sale could be known and before any future material events actually occurred. Could someone explain how this works?
Did you read the article? From the article: "One thing to keep in mind is both Ms. Izurieta’s and Mr. Becker’s 10B5-1 plans were adopted just a month prior to the sales occurring, and these transactions appear to be one-time in nature. They’re arguably open market sales masquerading as 10B5-1 transactions."
Please don't comment on whether someone read an article. "Did you even read the article? It mentions that" can be shortened to "The article mentions that."
You're required to preregister stock sales, but you can cancel those preregistered plans anytime, so it's possible to get around it by filing and canceling often.