It is a little contradictory, isn't it?
On every tractor I've been on the PTO rpm is not full rpm. There is usually a couple of hundred rpm to spare above the PTO mark. What I did with mine is that during the break-in period I backed off another 200 - 300 rpm while mowing and just took it a little bit slower. I never saw any difference in the quality of the cut. I also did other work with it that didn't require high revs and soon racked up the 50 hours. I honestly don't know if it did any good or not but it made me feel as if I was complying with the manufactures instructions and gave me a certain peace of mind. Also, I think it is more important not to let the engine labor or lug down during the break-in period rather than watching an absolute value on the rpm meter. JMO.
Now, the M5700 at the farm was thrashed from hour one and it hasn't affected it at all.