$\rm SO(10)$ grand unified model restores the parity symmetry lost in $\rm SU(5)$ model

Question

It is said in Lie Algebras in Particle Physics 2ed - From Isospin to Unified Theories (Georgi, 1999) p.285, Georgi said that

$\rm SO(10)$ grand unified model restores the parity symmetry that was lost completely in $\rm SU(5)$ model.

However, it seems to me that the spinor representation 16 alone in $\rm SO(10)$ model breaks the parity symmetry. Can experts clarify the conflict?

This post imported from StackExchange Physics at 2020-12-01 17:42 (UTC), posted by SE-user annie marie heart