How does the fork "know" that it is attached to an ebike that weighs a bit more than a clockwork bike?
The fork will be designed to have a max (rider + bike) weight in mind from a stiffness and strength viewpoint to withstand static and the huge range of dynamic loading. What I'm struggling to identify is what physical or engineering laws state that a 120kg (bike +rider) combo will affect the design of the fork if the proportional split between bike and rider was a variable?
An eBike’s moment of inertia about the bottom bracket / motor is higher because of the massive battery. So the fork will ‘know’ because the head tube is moving less. The rear shock should feel a bit less from a front impulse. I would also expect that an eBike rider would feel a bit less hand shock from a front impulse.
That said, I can’t understand why an eBike-specific fork is necessary; the tune for my Fox 36 / Avalanche fork from my human-powered bike feels just as good on my eBike.