As stated, "Spider-Man's ability is intended to replace his attack. He would be unblocked when the defending player declares blockers, could use his ability at the same time as a 'when blocked' ability, and then would go to the Used Pile."
I'm not sure what this means. The reason I ask is that I take "He would be unblocked when the defending player declares blockers" to mean that regardless of him being assigned a blocker, he can use his ability.
Can he use his ability if blocked now?
Please clarify and thank you.