The researchers explain this bending by Pauli repulsion between thefrontier orbital on silicon and the one on the arene. This repulsion is loosely related to the Pauli exclusion principle in which electrons in two filled orbitals tend to repulse each other at short range because they cannot occupy the same state. The frontier orbital of silicon can avoid alignment and overlap by this bending mode.
Only problem with this explanation is that the phenyl group flips towards the silicon lone pair. Simply flipping away would also put an end to steric concerns