[Kameron8]

Currently, hitting a resist while stunned does not refund 3m as the status indicates.  It instead refunds 7m, and does not bestow Stun Immunity.

To replicate:

1.  Have a mage with Galren, Stone Dragon, and Air Pressure.  PvP someone with 30+% wind resistance.
2.  Use Stone Dragon to set rocks beside the opponent.  Then use Air Pressure, making sure to hit the target while also throwing the rock at them.
3.  Note that the rocks move before the damage is dealt(?), and the resisted wind damage ends the stun instantly.  
4.  Observe that the stunned (now recovered) enemy has 7m.

[Kameron8]

This can still be replicated in the current patch/the test server patch. I checked to ensure this wasn't an air pressure specific interaction, and can confirm that hitting some other resist after the fact will still cause the stun to dissipate without Stun Immunity, and without reducing Momentum at all.