Are you seeing any updates to RHEL 6 published in Decmeber 2020 or January 2021 from your developer subscription?
I have no RHEL 6 systems at all, but I can access "Red Hat Enterprise Linux for x86_64 - Extended Update Suppport" for 6.7 so I guess I the dev subscription has access to it.
Yet, this is still the old dev subscription and it's limited to 1 phisical host/16 VMs for pure non-prod purposes.
Best Regards, Strahil Nikolov