I still believe (anyone can correct me if I'm wrong), that the Extended Life Cycle Support (ELS) for the 11th year of 6.10 is *NOT* included. To get that additional extention to the lifecycle still needs to be purchased.
I think you are right. As far as I remmeber even a regular customer won't have access to the 11th year unless paid for that.
Still, the dev subscription provides enough to keep a RHEL system up and running for 10 years (if nothing changes ... ).
Best Regards, Strahil Nikolov