As of https://bugzilla.novell.com/show_bug.cgi?id=164199:

KDE only sets the core pointer. Let me paste what Egbert said:

Comment #11 From Christian Boltz 2006-06-08 05:04 MST  
Stephan, I just tested the described scenario (laptop with synaptics touchpad +
external mouse) and set the mouse to left-hand in kcontrol.

Results:
- the touchpad was switched to left-hand correctly as expected
- the external mouse was still in right-hand configuration :-(

-> KDE should set the left-hand setting on _all_ mouse-like devices, not only
on the primary one.

Comment #12 From Stephan Kulow 2006-06-08 05:14 MST  
Egbert, KDE simply calls XSetPointerMapping and I don't see a way to make an
explicit "for all devices". Is this a X bug or should KDE do something more
fancy? 

Comment #13 From Egbert Eich 2006-06-08 06:49 MST  
This depends on what you do. If you have attached the second mouse as a second
input device and use the SendCoreEvents config option your XSetPointerMapping
will only act on the real core pointer not on the device that acts like one.
Please keep in mind that this was ment to allow extension input devices (such
as touch pads) to also generate core events (ie. manipulate the core pointer). 
You can change the button mappings of each extension device using
SetDeviceButtonMapping from the Xinput extension.
Unfortunately there is no way for a client to find out which input device also
sends core events. This option is an XFree86 DDX option and doesn't allow to
find out which device generates core events. 
With ListInputDevices from the Xinput Ext. one can find the current core
device.

Comment #14 From Stephan Kulow 2006-06-08 06:52 MST  
I read this so that the second mouse is configured wrong - i.e. not as the user
expects?

Comment #15 From Egbert Eich 2006-06-08 07:09 MST  
Right! 
XSetPointerMapping *only* acts on the core pointer device. You can use
XListInputDevices to get all other devices and SetDeviceButtonMapping to remap
the keys to the user's expectation. The big challange for you is to find out
which mice are configured to send core events (and thus would need to be
'fixed').

Comment #16 From Azerion Fagonda 2006-06-08 07:22 MST  
May I add that the is a chance that the user does not want the same
pointer-speed on the touchpad and the mouse...So if it is possible that you get
2 tabs in KDE with both 1 settingscreen for a device. Probably that will make
things even more difficult :P