Why does Words with Friends say I can make more points?
Solution 1:
I found this information online :
35 bonus points are awarded whenever a player uses all 7 tiles on their rack in a single turn.
That would match with the advice that the game gives you.
Solution 2:
According to this board editor you could have played BOATIES, BONIEST, BOOTIES, and a few other words for 53 points from the center tile.