a prop is often the most heavily stressed part on the whole
airplane,

From an engineering standpoint -

A light plane propeller, whether wood or aluminum, is about 1/8 inch
larger in diameter at cruise than when standing still due to
centrifugal acceleration. Consider also that a prop is an essential
non-redundant monolithic structure, which if aluminum, is made of a
material (2024-T3) that has good tensile, but mediocre fracture
toughness properties. In operation it is subject to very high-cycle
bending fatigue due to torsional resonances.

Fracture toughness is a measure of the crack propagation resistance of
a material. As a fracture toughness example, compare the tensile
strength of cellophane vs shrinkwrap with and without a tiny transverse
slot cut into it.
Props are highly stressed and must not be treated casually.