The acceleration settings in Synapse are implemented using Windows input APIs, which were removed from Windows 10 by Microsoft itself.
that means moving the slider, even in Synapse 2, would have no effect on your mouse pointer's acceleration and windows will get "raw" input from the mouse in either case.
You'll have to recreate it with third party software OR go the extreme route, using windows 7 and a legacy synapse version, like synapse 2. That should work.