trying to understand how Reed Group (my work's administrator of disability) view PCS. I don't understand the second line of this sentence. Are they suggesting malingering? If no why do they call them mild.

Factors Influencing Duration

Length of disability will be affected by the level of concentration required on the job; the severity of the concussion; and any complications such as brain damage, symptoms of post-concussion syndrome, and mental impairment. Mild complaints associated with MTBI and post-concussion syndromes may challenge return to work efforts.