The 2,000 fpm rate of climb limit is there because at light weight and maximum power, it was not possible to measure longitudinal static stability - not that there might not be some, but the rate of climb was so high that it was not possible to stabilize on the airspeeds long enough to get the necessary data. The limitation allowed that measurement to be made.
This would be one of the few times when I would say 'Be your own counsel' on a limitation.