Of course! All propellers flex. What is often missed is that flex is a good characteristic. For example, if a prop flexed under the load of acceleration, it would actually be reducing its pitch, which in turn would produce a faster acceleration. A problem would occur only if the prop failed to return to its specified pitch once up to speed with the load reduced. The measurement of this two-way propeller movement is called “yield.”
The question people should ask is: “should I be concerned with a low yield number in a composite and aluminum prop?” In this regard, the yield numbers for aluminum and composite are about the same and high enough to handle the loads designed for. Stainless (being much stiffer) has a higher yield number and is well above basic requirements.