There's plenty of attention on the Github meta issue about the lack of IPv6 (https://github.com/orgs/community/discussions/10539) so anyone who even glances at customer requests should be aware of the issue at the very least.

They also did offer IPv6 availability for a short while as a test, but that was quickly shut down, so there is probably a technical issues they can't figure out or they would've kept the trial system running for longer.

Either way, Github isn't communicating, so it's hard to tell if this is indifference or incompetence. As an end user, the distinction doesn't really matter.