But I didn't understand if they support the same container spec from docker or not: i. e. will a container created with docker run on apple silicon now?

It's still running in a tiny Linux VM. One VM per container if what I've read is right...

It's running on Apple Silicon because it's only available on Apple Silicon. Docker/orbstack/lima/etc are also running on Apple Silicon when your Mac is an Apple Silicon Mac, so I didn't quite get the meaning of that last one...

If you were trying to say it's running natively without a Linux VM though, it's wrong insofar as it's not running on a single shared VM as the other solutions do but it's still using Linux VMs.