>>23387492The flying type isn't removed on the second turn though. The pokemon is simply grounded. We see this when we see iron ball or gravity in effect. The flying type would still resist fighting and be weak to ice for Instance, it simply loses the ground immunity.
Furthermore flying didn't seem to have a consistent type interaction on the first turn with thousand arrows. It hit skarmory, tropius, and wingull neutrally. Each of them have a subtype that interacts differently with ground, so we can safely say flying doesn't have a hidden resistance to ground if it loses the immunity.
Thousand arrows simply seems to hit all flying types immune to ground neutrally.
I wonder if they'll change it in Z, if it's purely an oversight.