Metahub found something that may have vindicated me:
Unannounced Move Change with HUGE Implications
Another insane thing we found in the code was something we had to test repeatedly before we believed it. As it turns out, despite the tooltip still showing Swap-In Stun at 66%, the code shows something very different. The code shows Swap-In Stun has a 100% chance of succeeding, not 66%.
And sure enough, we never missed a Swap-In Stun in our testing. This has MASSIVE implications for dinosaurs like Edmontoguanadon, Maiasaura, Pachycephalosaurus, even lower tier dinosaurs like Tenontosaurus, Edmontosaurus, or Iguanadon.
If this isn’t a mistake, and it actually sticks, that means Swap-In Stun is potentially just as powerful as Swap-In Dodge and Swap-In Invincibility. Not only would this counter a Swap-In Shattering Rampage from a Dracoceratops or DG2, but this guarantees a FREE swap on anything with this swap-in action.