When I did my physics PhD 5 years was the advertised time to finish, but it took most people 6 or 7 years. The faculty/administrators who worry about such things knew it was a problem and were actively working to fix it, so maybe they've made some progress? The whiz kids at certain institutions got out more quickly of course, but that was not the norm. The programs were being accused of false advertising by not "updating" their time-to-complete numbers.
That was the path I followed in physics, though I took a bit longer to finish. I had friends in fields (e.g., psychology) where they had to do an interim masters. In my view, the result was that the masters became a hoop to jump through, and one that saddled the literature with studies that weren't really very meaty.
Personally, I'm leery of anything that makes the degree take longer. The reason is that grad students face the constant risk of things that can force them to quit without anything to show for it. For instance your advisor can spontaneously quit, or for that matter, drop dead. Your research can get "scooped." You can run into health or family issues.
>>> Most professors are not trained teachers.
Most college teachers are not professors. A few years ago, I taught a couple of college courses for a semester. If you want things like teacher training, then you have to make college teaching remotely career-worthy.