Yeah, my lines referring to Deku's prowess were sarcastic. He doesn't think highly of himself, but he instead thinks little of All Might's might. It's like he worships All Might's shadow, but doesn't ever want All Might to do the only thing the man wants to do, in fear of his greatest, undefeated hero of justice actually not being able to pull through. That's remarkable lack of faith resulting in hypocrisy. He believes in All Might's message but not the man behind the message.

But then again, I guess that goes along well with the personality of a bullied person with little self-confidence.