The angle that matters does change as you move the drone (yaw, pitch or motion).
Mathematically, there is a plane defined by the sun, subject, and the camera. There is another plane defined by the axis line of polarization in the filter, and the subject. The filter's maximum effect is when these planes are perpendicular at the filter; the filter's minimum effect is when these planes are aligned parallel at the filter. And when I say "subject" I mean whatever surface (leaf, shingle, wave, window) is in view for each different pixel in the sensor.