Even worse than that, they need to be able to make an arbitrary container from an arbitrary attacker-provided Dockerfile, or make fairly arbitrary calls to the Docker daemon (in which case you've already lost).
They're rather uninteresting for anyone self-hosting containers as the runc vuln doesn't offer a way to escape from within an already running container, while the BuildKit vulns all have fairly odd preconditions or require passing untrusted input. Quite the annoyance if you're running some kind of public cloud or public CI/CD service, though.