Actually, they previously released cars every 2 years (B5, B6, 6.1, 6.2) several months after the Worlds. The announcement of the B6.2 was January last year.
I guess with money not being spent for holidays, theater shows, festivals or amusement parks, people sought other means to spend their money. I would not be surprised if Associated ran out of stock sooner than they thought and saw a chance to keep sales up in 2021
Perhaps I'm being a bit blunt but I'll just say it: to me it seems as if they tried hard to put new features into the car but they hardly qualify as meaningful upgrades if you have a B6.2 right now... Probably you're better off putting some training laps in if you want to improve your lap time. I know for this and many more reasons, I am!