Most likely the culprit is someone on their staff that broke their NDA contract, but the DMCA is about stopping the proliferation of copyrighted material. They are misusing the DMCA because it has higher discovery/subpoena ability.
Can an NDA be used as justification for a DMCA? Has it happened before?
> but the DMCA is about stopping the proliferation of copyrighted material.
If the videos posted to twitter were just summaries and not actual video of the unreleased show it seems unlikely that there was any copyrighted material being proliferated