Scott is indestructible: If G#012 Cyclops Sentinel is on the map, Sentinel Head can't be KO'd except by a critical hit.

Does this mean that even though the Sentinel Head does not have Willpower or Indomitable, if you push it, it will remain on the map and not be KO'd?

Sounds right to me.

Ugh! That is OP!

Not really. Not having Protected: Outwit or Pulse Wave means it dies pretty easily. But sure, otherwise, it's staying on that map.