The Fear rules could be read as saying that surges spent on overcoming Fear give the attack the "overcomes X ranks of Fear" trait, and it doesn't matter how many times you have to overcome X ranks of Fear. The rules say that you have to spend surges and that the surges spent in this way can't be used to activate other abilities, but it doesn't say that you are actually spending the surges on anything in particular. In fact, without the last sentence, you could technically spend 3 surges on +1 damage and that would also let you overcome Fear 3 as a side-effect.
"When attacking a figure with the Fear ability, the attacker must spend 1 power surge for every rank of Fear the figure possesses. If the attacker cannot spend enough surges to overcome the Fear ability, the attack automatically misses.
Surges spent to overcome this ability are wasted and cannot be used to activate other abilities."
Now, again, I think the most natural and straightforward reading is that you are spending the surges to overcome a specific source of Fear, but the text doesn't actually say that. It just says that the surges have to be spent , and that the same surges can't be spent on other abilities .