Geoff, you are right - I am not familiar with the type and maybe the quote would appear more logical in a wider context.
What I would say is this: For a CAt B procedure, the only pre-requisite is the ability to hover IGE AEO. Nothing is guaranteed in the way of OEI performance either for a rejected take off or continued (or attempted continued!) Take off. Therefore, it would make sense to operate the aircraft at the most efficient Nr when AEO, which seems to be 100%, as this is the only flight regime being recognised by the RFM.
For a CAt A procedure, everything is predicated on the subsequent OEI performance, so it would make sense to operate such that in the event of an engine failure, the aircraft then enters the optimum OEI conditions. It would seem that the natual Nr decay for this type (as quoted) is about 2%, therefore setting 102% for AEO ops would place the aircraft at 100% in the transition to OEI.
Of course, at the end of the day it all depends what you do with the lever after the failure and I'm assuming the quoted decay is the normal result of leaving the collective position alone.
I hope this ties in with your dilema?