[Bf-committers] Why has "CTRL y" been changed to "CTRL SHIFT z" ?

[Jass]

Am 16.04.2011 03:49, schrieb Ρυακιωτάκης Αντώνης:
> Actually typing Ctrl-Y with one hand can be more difficult(You have to
> stretch your hand and find the key on the keyboard). Ctrl-Shift-Z allows you
> to quickly undo and redo without thinking about it too much. All three
> buttons are nearby. 
The argument does not fully count on german keyboards where y and z are
exchanged. Try to type ctrl+shift+y on your non german keyboard to see
(feel) what i mean ...
> It's all a matter of habit of course but if both are not
> permitted at the same time I vote for Ctrl-Shift-Z.
Which leads back to my question ;-) Why is it not permitted to support 
both ctrl+y and ctrl+shift+z at the same time in the blender-standard ?
Is there any special purpose usage for ctrl-y in blender which i overlook ?