Inbox messages that announce updates routinely invite you to check out the forums for more info. If you don't read the forum posts, that's cool, but CG keep telling players to look at information on the forums with in-game messages. It's also neither a new thing nor unique to SWGOH that some information about a video game is not available from inside the game itself. Patch notes, update text posts--this is common and accepted practice in the gaming space and has been for years. If you are the kind of purist who just refuses to look at the forums on principle, that's on you.
Detailed information about anniversary quests and the LSTs awarded by those quests was provided well in advance.