Ah - this makes sense (my guess about Comcast in the other thread appears to have been wrong).
It's interesting to see how so many different ISPs do so many different things with their IPv6 rollouts. It's going to be nice a few years down the road once the industry settles into standards like it has with IPv4.
Hopefully by then Mikrotik will decide which "advanced" features to implement in IPv6 to accommodate the standard, since they don't want to spend any time developing features that don't gain traction in the industry.... like stateful host assignment capabilities in DHCPv6 server or prefix-translation NAT - sure THOSE features will get abandoned the day after Mikrotik decides to implement them.