Sure enough, it showed up. I don't know why there was a delay as I already had all 9 boards unlocked in all 4 modes, but the trophy appeared roughly 10 minutes into my next play session after restarting the game. I decided to go back and start getting scores on boards that I had unlocked but not played yet and it showed up in the middle of playing a board.
Now to last for 2 hours for that trophy.
Very addictive game and fully enjoying it.