  Previous full-lifetime simulations of single-star multi-planet systems across
all phases of stellar evolution have predominately assumed coplanar or
nearly-coplanar orbits. Here we assess the consequences of this assumption by
removing it and exploring the effect of giant branch mass loss on the stability
of two-planet systems with small to moderate non-Kozai (<40 degrees) relative
inclinations. We run nearly 10^4 simulations over 14 Gyr for F-star, A-star and
B-star planet hosts, incorporating main sequence stellar masses of 1.5, 2.0,
2.5, 3.0 and 5.0 solar masses, and initial planetary semimajor axis ratios that
straddle their three-dimensional Hill stability limits. We find that the
near-coplanar assumption can approximate well the stability frequencies and
critical separations found for higher inclinations, except around strong
mean-motion commensurabilities. Late instabilities -- after the star has become
a white dwarf -- occur throughout the explored mutual inclination range.
Consequently, non-Kozai mutual inclination should not be used as a predictive
orbital proxy for determining which white dwarf multi-planet systems discovered
by Gaia should represent high-priority follow-up targets for the detection of
metal pollution and planetary debris discs.
