It turns out that for various internal technical reasons, the value of the new menu toggle point MUST be less than 768 to work correctly.
The goal of the new option was to allow short regular menus to be used on mobile devices.
The next release will not allow values >= 768.
The goal of this was NOT to put a mobile menu on an iPad. An iPad is very hardwired as a desktop device, and there is unfortunately no way to change that.