Here are my reasons:
1. Akainu was lunging forward to get Jinbe but was then driven back. He had his hands full already. Akainu was literally about to execute the fish, doesn't really scream FS and reform lmao
2. The question marks on the panel, Akainu was surprise attacked
3. Signs of visible distress including clenched jaw and black lines surrounding him indicating he was struck
4. "Kuu.. Ahh, how irritating" yeah you're just bs yourself if you don't see this as a sign of pain. There's no reason for Akainu to be irritated if he managed to reform
5. "Haki users, huh" again its retarded for him to say this if they didn't actually hit him
6. Also note how the wave of Marco's attack increased in size