You don't want a shorted coil under, over or near your
inductor. RF people use lightly doped trap rich substrates
(high R) underneath a buried oxide (infinite R) to tamp
down eddy losses which de-Q an inductor.
"People do" stupid things for stupid reasons, on occasion.
Small signal inductors at RF are not going to spray a lot
of magnetic field. It can be enough to matter, to on-chip
circuitry (just like any other interconnect-radiator; don't
forget about longitudinal AC currents in straight wires
either, seen those hose a GPS LNA with clock signal harmonics,
thanks to a customer's lame ("low cost") frequency plan....
I believe you're best off with some "substrate engineering"
(or simple selection) like I describe. Or, you declare the
presence of RF magnetic fields and make it the customer's
module / PCB construction problem.