Why one can Control+Option+U to edit a cell on Numbers? It has been noted there are two ways to edit a cell on Numbers, Option+Enter seems to do the job.
But still there is Ctrl+Option+U, why?
They behave differently. If the cell has a formula inside, ⌃ Ctrl  + ⌥ Option  + U  erases the formula and makes the user type over it while ⌥ Option  + ↵ Return  allows the user to edit the formula as well.