I've seen that, too -- my guess is that this indeed is a bug: the ASA 5505 internally has switch ports only, which are kept separate by using VLANs. Apparently, the 5505 SNMP agent is smart enough to show the VLAN interface names and addresses, but shows the traffic data of the main interface only (of which there is only one).
On the other hand, the ADSM somehow can display correct traffic statistics for ASA 5505, but I do not know how it obtains the data.
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...