From:
https://www.traumaticbraininjury.com/mild-tbi-symptoms/These symptoms may not be present or noticed at the time of injury. They may be delayed days or weeks before they appear. The symptoms are often subtle and are often missed by the injured person, family and doctors.
The person looks normal and often moves normal in spite of not feeling or thinking normal. This makes the diagnosis easy to miss. Family and friends often notice changes in behavior before the injured person realizes there is a problem. Frustration at work or when performing household tasks may bring the person to seek medical care.
These injuries often go undiagnosed or diagnosis is delayed, because the symptoms may not be immediately evident.
(IOW, initial reports may not have accurately reflected these instances of concussion because the injuries were not yet evident, not because there was any effort to downplay the injuries sustained.)