[Ctrl]+[Enter] does not work when changing object definitions

Sadly, another problem with the keyboard shortcut [Ctrl]+[Enter]: If you already defined an object and made use of it, you cannot change its definition from symbolic to numeric via [Ctrl]+[Enter], but only by clicking the Numeric tool.

Steps to reproduce (CAS):

• Type "a:=0.5" in cell 1 and evaluate with normal [Enter] -> Output: "a:=1/2"

• Type "a+1" in cell 2 and evaluate in any way ([Enter] or [Ctrl]+[Enter], whatever you like)
• Go back to the input line of cell 1 and try to re-evaluate it numerically via [Ctrl]+[Enter].

You would expect to have the output of cell 1 change to "a:=0.5", but that doesn't happen. The only way to achieve that is to click the "Numeric" tool.

Of course, that is just a little example without much of a problem, but it gets a lot worse when your object is not a variable, but a rather complicated function. If you first define it symbolically, make a few calculations and then decide that you would like to change it from symbolic to numeric, that doesn't work without clicking in the toolbar.

Why is that so?

Why can't [Ctrl]+[Enter] just simply ALWAYS do the exact same thing as what would happen if you clicked the Numeric tool?