It all comes down to the definition of 'damage'. Equating damage with superficial damage is just an irrational, and more than anything else, oversimplified way of looking at it.
A new study in the field of neuropathology, for example, says that CTE is not related to concussions but rather is related to getting hit in the head in general. If the study is to be believed, it sure seems to me like N'Gannou came out of the fight with more potential areas of degenerative brain tissue present.
Also seems to me that the sort of damage that will presumably never regenerate is more meaningful long-term than getting your eye smashed.