The 5 degrees is the sweepback on the normal Hart wing, so if that was retained on the trainer then they used the wing outer panels unchanged and put up with half that as a misalignment.

I’m still not clear whether they pivoted the wing about the front spar, thus needing to do something about the rear opening up a gap, or pivoted about the rear spar, thus needing to shorten the main spar. The former seems more likely, but if so did they realign the mating surfaces by extending the rear spar inside the wing, or just put some bridging structure?