I am seeing 1mbps rates on BSSIDs that have lower rates (1,2 and 5.5mbps) disabled. I am running 6.3.1.2
TAC says they can replicate in lab and looking into it. Curious if your output is similar. This is an example of our Eduroam SSID out of one WAP (show ap active ap-name xx):
80211g ESSID eduroam Stats
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Parameter Value
--------- -----
(truncated)
BSS Tx Rate 1 mbps
BSS Rx Rate 1 mbps