Indeed, the original logic is backwards ... I've owned a MK1 ZS EV for a couple of years now, just upgraded to the MK2 facelift.
KERS is remember wherever it is set & in my case, this has stayed permanently at 3, the maximum regen breaking. The title syas it all "regenerative breaking" meaning the disc pads are not used while slowing down, only in the final moments should we need to come to a complete stop, ie, no 'one pedal driving' but close. KERS 1 setting at the other extreme provides no regerative breaking & therefor always requires use of the break pedal. This is the quivalent of an ICE vehicle.
So to minimise the use of break pads and to obtain better battery economy, always use KERS3.