High Priority CIR link test question

Seeing something odd.  I've got a PMP450 AP and SM sitting on the bench here.  10mhz channel on 13.3 firmware so we can get the 5ms frame.

20mbps limited SM, BTW, but running 'link test with bridging' or 'RF link test' that doesn't seem to come into play.

So I see close to the speeds I expected.  But with High Priority CIR set to 200kbps up and down, the link test with "High and Low Priority VCs" enabled doesn't make any sense:

Link Test with Bridging

VC Downlink Uplink Aggregate Packet Transmit Packet ReceiveActual Actual

Total Both VCs 43.55 Mbps 12.14 Mbps 55.70 Mbps,  4514 pps 9772 (977 pps) 35377(3537 pps)
136 (High Priority) 43.46 Mbps 12.02 Mbps 55.49 Mbps,  4503 pps 9736 (973 pps) 35308(3530 pps)
18 (Low Priority) 88.47 kbps 122.88 kbps 211.35 kbps,  9 pps 36 (3 pps) 69(6 pps)

When I run link test with MIR (limited at 15mbps down and 5mbps up) I get a wide range of results, from 5 to 12 mbps down in High Priority, 3-5 up, with the remainder in low priority.

Have I missed something?  Is the link test with HighPriority broken?  I've not tested 'user' throughput yet to see if the same proportions apply there.