Tim
You are correct, the primary reason for the change was that there had been some major mistakes in the tech logs with the HH:MM arithmetic that could have ( in one case ) resulted in the aircraft overrunning a maintenance check by 17 hours.
There had been very occasional incidents of tailwinds in both directions but these have been few and far between.
The fact that Lycoming recommend flight at 60 % power for longest engine life and the airborne time is very close to take off to touchdown times is at 65% power results in the aircraft being flown at the most economical settings for both the club and the renters.
Those who use higher power settings will pay more and the engine life vs actual time in the air will be reduced to take account of the reduction in engine life resulting from high power settings.