GPS is usually accurate up to 1m or 2m. When converted to kmph that means you can easily have an error of 5-10 kmph. So most likely, the 135 kmph is due to a GPS error and actual speed might have been around 120-130 kmph.
C &M vol 1 standards are not very strictly followed now as the guidelines were decided way back when the Rajdhanis were first introduced (in May, 1969) . Since then the technology has improved and many of the constraints mentioned in the standards can be relaxed now because of availability of better equipment and rolling stock. In fact even on high speed certified 'A' class sections like Delhi - Howrah , hardly...
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60% of the route strictly follows the C & M standards. And the standards are mainly for track conditions, ground conditions around the tracks, gradients and curves etc and there aren't many specifications for OHE's in these standards. Even on 'A' class tracks fit for 160kmph, e-locos may be restricted to lower speeds due to OHE conditions.