Before the last attack all damage Rocks took was healed, just as Harald.
The difference is that in Harald's case, not only wasn't a 2vs1, but Harald actually came back to his senses. And not only that: Loki was 17 YO and doesn't seems It was even that damaged. After getting Ragnir and the fruit, the fight was quite one sided.
We can say It was exaggerated, but this was incredible.
All the damage rocks took before the final attack was not heal.
We did not see any regen or was it mention that rocks heal.
What was said was he was using his CoC to cancel out the attacks done by that garp and roger .
So why would he need to heal when he has ben cancelling out the damage ?
That is why they said they had to do one big attack because rocks was not getting damage .
The fight was loki giving him 4 hits and he healing from them .
If we going with what Gaban said it was not strong damage since Harald heal fast .
Then harald allow him to kill him .
Read over chapter 1165 rocks had no damage to heal because he was cancelling out roger and garp attack with his CoC .