Mach does not back off a set distance, so no it is not hard coded. What Mach does is moves to the switch and when it is broken it reverses until the switch again closes and then stops.
If you are having problems with the switch seemingly closing before Mach has backed fully off of it then it would seem you either have bouncy contacts or electrical noise. It is best to get rid of these problems by either having good quality switches (for the bounce) or shielding and properly grounding the wires to the switches (electrical noise) You can however increase the Debounce Interval which is on the General Config page and this may help, although it is still in my opinion best to get things sorted properly.
Hood