In my university the first part ("successfully proposing a dissertation to a specific committee") was called the preliminary exam ("prelim"). In principle, you should do this decently early in your thesis. In practice, many advisors would tell their students "Go do 90% of the research and when you're close to defending, do the prelim". They didn't want to commit to a project and later fail to achieve it.

So with those advisors, it was normal for people to graduate six months after the prelim (because the department required a minimum of 6 months between the prelim and the defense).