The threshold for the pitchwheel is a feature that is intended.
Explanation:
There are plenty of old/crappy Midi Keyboards out there. They do not longer center the pitchwheel exactly and return Midi pitchbend values that are slightly off. This can make synthesizer plugins be out-of-tune, expecially if they are set to a high pitchbend range like +-12 semitones. The threshold in Icarus in the center of the pitchbend fixes this problem.
I'll check out if it is possible to lower the threshold a bit for the next update.
You can get a more fine pitchwheel resolution if you change PitchWheel+-12 to +-2 in the top left of the synthesizer.
Not sure why my previous comment has been deleted.....?
Since this is the feature request thread; I would like to see an option to set a pitchwheel offset/threshold