Very much agreed. Keep in mind, too, that life happens when you are spending this long in a program - students may take time off to have children/spend time with their families, etc.
I would say that's a minority of students. I hear this stuff all the time when we're dealing with applicants, because it sounds nice. The reality is I'd say these sorts of issues are not true for a majority of the 9+ year students I've talked to. **** happens. But, IMO, the **** should push you from being a 7 year to an 8-9 year student, not expecting the MD/PhD program to take 8 years and then when **** happens it pushes you to 9-10 years. If you go in with the attitude that this should be 7 years and your program has the attitude this should be 7 years, the average tends to be closer to 7 years.
How long the PhD takes (which is the main variable here, since med school cannot usually be shortened) depends more on your choice of PhD advisor/committee/thesis project than the institution. Oh, and of course it depends on how hard you work and a lot on how lucky you are!
Numbers are averages for a reason. They reflect on the institution. The institutional average between schools vary as much as a year or more, and this in my opinion should be noted in the minds of the applicants. Of course there are going to be individual fluctuations that a program can not control. That goes without saying. However, the number of requirements from a MSTP or graduate program (coursework, TAing, additional clinical rotations, etc) is something that you should pay attention to.
But this varies within schools too. I'd say some grad programs here view the MD/PhD as a minimum 8 year thing and some view it as a minimum 6 year thing. Of course a lot of this is up to the invidual. But, if the individual has to do 2 years of classes and 6 months of TAing, how the heck do you expect them to finish in 7 total? At some MSTPs a full year of TAing undergrads is required. This is a total waste of time IMO, but regardless of your opinion this is going to knock back the program's average time.
A 7.5 year program, for most schools, would mean you get your PhD in 3.5 years. While this is not unheard of, it is a bit optimistic. 4 years for the PhD is a reasonable expectation
At many programs the MD portion is shortened to 3.5 years or less by cutting out much of 4th year. The only places where this isn't true are the places that still require a 6 month rural/primary care rotation even from their MD/PhD students (wtf?). This means at most programs it's more like a 3.5/3.5 for a 7 year program or 3.5/4.5 for an 8 year program. Is a 3.5 year PhD optimistic? Sure. It's what I'm doing. But, don't forget I did all my rotations before starting grad school and took several courses before starting grad school. I didn't even really have a year of courses to take when I hit grad school. I started on my thesis project very shortly after I hit the lab. My mentor is very MD/PhD friendly. These are the sorts of things that are the keys to getting done soon. But, you have to be proactive on your end, and you have to think critically about these things rather than being passive and just hoping it works out. Of course some things are out of your control, but if time to graduation is important to you, the MSTP you choose, the mentor you choose, the graduate program you choose, the project you choose, they are all within your control.