Because it's spinning blades among manufacturing tolerances you also have to account for the blades expanding when rotating at high speed, and possibly working with 40-50 °C air from the components
In their own description of Sterrox® LCP they say it has "extreme tensile strength, exceptionally low thermal expansion coefficient, high environmental inertia and excellent dimensional stability". With such an advanced polymer any deformation in operation has to be a rounding error compared to the manufacturing tolerances.