Claiming repeated minor head traumas are more dangerous than a single major head trauma that results in loss of consciousness is misleading. Additionally, I read the original Mayo Clinic article you linked and couldn't find the claim you listed.
According to the Mayo Clinic's page on Traumatic Brain Injuries (TBIs), any blow to the head that causes behavioral changes necessitates an immediate visit to the doctor. But if there are symptoms specific to TBIs like loss of consciousness, the Mayo Clinic advises seeking emergency medical care due to the dangers associated with a TBI.
While brains with CTE are found to have an atrophy-causing protein, this atrophy equates to the atrophy associated with Alzheimer's disease or dementia which people can live with for decades.
Though some TBIs are referred to as a "mild TBI", the Mayo clinic says "The terms 'mild,' 'moderate' and 'severe' are used to describe the effect of the injury on brain function. A mild injury to the brain is still a serious injury that requires prompt attention and an accurate diagnosis." Every TBI carries the risk of potentially life-threatening symptoms like seizures, repeated vomiting, inability to wakeup from sleep, and more. All of these symptoms can immediately threaten the lives of TBI sufferers, whereas CTE's effects take place over a long period of time.