The rear offset is unique and is probably because the Jalpa (and Silhouette) got flares around Urraco suspension and brakes, so the extra width had to be built into the wheel offset.

Btw, the width of the front wheel is also 7½“, not 7”.
Also be careful interpreting the listed front wheel tire/ fender clearance. If you turn the wheels and go over bump, this can easily be reduced to zero.