He did eat it.
He healed within a week just like the rest of scabbards and Luffy though not 100% but still more than enough.
He didn't need a month or half a year, he was not declared a special case due to this.
If he can take that sort of damage then it's either there isn't much difference between zero Haki Bagua and ADCoc Haki Bagua or Kinnemon has definitely top tier durability.
Or it could also mean Kinnemon wasn't amping himself up at the same level as when he took the thunder Bagua.