You are missing the entire point of the oral defense while almost stating it. The existence of the oral defense is what extrinsically motivates the supervisor t

You are missing the entire point of the oral defense while almost stating it. The existence of the oral defense is what extrinsically motivates the supervisor to do their job well. If the student fails, the supervisor loses faces in front of their peers, which obviously they try to avoid. Removing the oral defense would massively reduce the quality of PhDs because supervisors will not do their job. Also in my observational experience in physics, a fair number of students (probably like 10%) get some sort of major corrections to their thesis. After writing this, I did a search, and in the UK, the number across all fields is 16% [1]. [1] https://www.lexacademic.com/blog/how-common-is-passing-with-major-corrections-from-a-phd-lex-academic-blog/ https://www.lexacademic.com/blog/how-common-is-passing-with-...