Some stuff isn't quite correct. Craniotomy is often used as a standalone solution to relieve pressure. It's the standard procedure to treat brain swelling, which among other things, can be caused by subdural hematoma aka a brain bleed. Which is one of the most classic life-threatening injuries boxers face. Assuming Morikawa, someone who actually is involved in the boxing world and knows these types of injuries, is inserting some realism here, and given the somewhat long-term progression of his condition requiring the craniectomy, the swelling is more likely.
After performing the craniotomy, they may or may not operate further to repair/treat the brain structure. Not every bleed or other injury needs surgical intervention, or it may also be deemed more dangerous to do so than to simply leave it be. Medication can be an alternative.
Whether he can return to boxing or not is very doubtful. When you perform a craniotomy to enable surgery or to just relieve pressure from fluid buildup, you can section a very small part of the skull. However, it's very unlikely in his case. His brain swelling would have likely required a very large plate to be removed, exposing a wide area of his brain and making it very likely he would face numerous complications and never fully recover.
Even if it was a small section, a craniotomy permanently compromises the integrity of the skull. Its unlikely any doctor would ever certify him fit for boxing ever again, given the risks, even if he had no other complications. But it's very likely worse than that. For more serious craniotomy, the original skull is typically not reused and a cast is used instead. He will also almost certainly face neurological problems...anything from headaches, memory problems, seizures, trouble speaking or focusing, personality changes, even early onset dementia, and more. Sometimes coma or death.
When you have such a procedure performed, the outcome is not comparable to just having TBI that didn't require surgical intervention. It's usually only done when the alternative is death, and excessive brain swelling is always lethal. I don't believe there's any published case of a prominent boxer able to return to the sport after a craniotomy, or an athlete in any other contact sport for that matter, for a related injury. Might be a rare few from non-emergency ones for unrelated surgeries. He will be lucky not to end up dependent on others for care for the rest of his life.
I'm not a doctor, but this is fact checked by my siblings who are, including specialists.
TLDR: Mashiba is absolutely done. It's not about what he wants, or what he's willing to risk. He'll be lucky to live a normal life after this.
