It would appear that aircraft with the Erla, one-piece hood, had the wire tensioner attached to the hood locking latch, and those aircraft with the earlier, three-piece canopy did not, as it was not needed. The earlier hood had a 'fixed' rear section (although this jettisoned along with the opening section for bale-out, taking the antenna mast with it), and therefore tension on the wire could be constant.
Whereas, the Erla hood opened as one piece, and requires some slackening of the wire to allow it to swing to starboard. The wire was only under tension if the canopy was locked in the closed position, which could only be done from inside the aircraft.