So is Jendon's ability a cost or a condition .
Cost: Jendon must 'spend' his attack against a ship or squadron to use his ability. Thus is he not attacking the ship/squad and can be countered?
Condition: To use his ability Jendon cannot then attack and cannot use his ability if he has attacked, whether or not he can is irrelevant.
Instead isn't a keyword for anything so its meaning is unclear. How does the stack work for using his ability? Declare attack->Don't->chose another squad->another squad attacks? Check that you can make an attack(not a step in anything or the rules btw)->Don't->chose another squad->another squad attacks? Can he use his ability if he moves during the squadron phase?
Now the only reason I bring this up is (different system I know) feedback array from X-Wing uses the same language but is a condition not a cost. Does anything in armada use this term "instead of attacking" and has it been ruled to be a condition or a cost?