Comment by bmalehorn

I ran this on a Linux laptop - it looks like it's running qemu-user-static:

    root        9934  103  0.0 125444  6664 pts/0    Rl+  12:25   0:12 /usr/bin/qemu-aarch64-static /usr/bin/gzip

So it might be that Docker already runs a native x86_64 Linux, then uses qemu-static binary translation.