A root canal on an infected tooth isn't wrong but the doc should know it may not work and should follow the pt closely, maybe daily, until it resolves. If it doesn't resolve or pt doesn't respond as hoped then investigate & change plan as needed. "Watching it" or "giving more time" is not acceptable if we're talking about a high risk situation.This was over 60 years ago and the story given to my mother may have been completely wrong but...
...that statement is particularly poignant to me. My mom had a root canal on a severely infected tooth. According to the doctors who eventually removed her left eye, the infection traveled to her eye and destroyed it.
Now, having a one-eyed mom does have it's humorous side but, frankly, I would have preferred if she had had vision in both eyes.