Fortunately the two of them are touching, and that's enough! When the key gets twisted, reality twists around them. Rather than Eight's method of teleportation that was like dropping them through a hole in reality, this kind of teleport is more like being in a droplet of water. It's very clear that they're moving, falling through some wild world, but they just sort of fall as the world reflects around them and then--

They're standing on the arrival platform that Luka had arrived on originally, the one that the braille-poles pointed back to with the label "Portal on it. It hadn't made sense, before, why it was named portal. But now?

This is where the ship's teleport landed. This is where twisting that key sent people back to.

And now both Gyre and Luka are left standing there, back in the garden, where they'd started.