> Force touch is no more a secret than the adoption of the right mouse button was in Windows 95.
I don't think you understand discoverability at all.
People know there's a right mouse button simply by looking at the mouse. They might not know when or where to use it but they can see the button and know it has a purpose. The button invites people to press it and they might randomly try it in various places to see if it does anything and discover a feature. The OS is irrelevant.
You can't see Force Touch. You don't know it's there until someone tells.