The manual of the Canon TS-E 17mm F/4 states that metering only works when the lens tilt and shift are set to zero (in the same position as a standard lens would be). Logically this implies that the meter indicator in manual mode would be incorrect as well.
What techniques then would be recommended to meter with such lens? Does the light entering the lens depend on the shift and/or tilt positions? If you meter from a highlight the the lens and camera straight, would that be still valid after tilt, shift and the orientation adjusted? (Obviously for reflective surfaces the answer to the latter is no).