I am curious as to whether the receiver "plumbing" downstream of the probe/receptacle is identical in all models. If this is the case then that seems likely that either:
1. The -A is saddled with a system that can only onload fuel from a boom at rates equivalent to that from a hose.
or
2. The -B/C is lugging around a weight penalty from the heftier pipework necessary to allow the -A to take proper advantage of boom AAR.
Has Australia made a decision on probe or receptacle for its -A models? The answer to the question above would seem fairly fundamental to that choice. There would be little point in opting for boom refuelling unless there is a substantial advantage in onload rate.