Hey, dev here — not sure what you mean. OrbStack currently ships an official build of Docker Engine 24.0.5, which is the latest version as of writing. Previous versions used Alpine Linux's build.
I did intentionally delay the update from 23.x to 24.x by a few weeks while I waited for things to settle, because last time I updated from 22.x to 23.x shortly after release and some users were hit by bugs that hadn't been ironed out yet.
Edit: Noticed that you edited your comment to say that it uses "Docker Machine" instead. That's not the case. OrbStack uses a nested architecture where it runs Linux machines [1]. There's a special machine called "docker" that runs a copy of the Docker Engine, but that's not related to the old Docker Machine project.