Wow, that's really different, as there are schools that arrange their preclinical curriculum much more "cleanly" than WashU, such as Baylor and USC-Keck. Their preclinical curriculums have caused their average board scores to shoot thru the roof, as their faculty tend to purposefully teach to the boards as well. They also get more "time" to study after classes are over to put all the info. altogether.
I think WashU tends to be more conservative to changing (which takes more logistical work on their part) to more student-"friendly" measures with regards to preclinical curriculum, teaching to Step 1, "time" to study after classes are over, etc. bc they know that when it comes to residency interviews, coming from WashU means a lot. They know already their "milkshake brings all the boys to the yard" due to being a research powerhouse, so they don't have to change.
With that said, if a student at WashU is in the top 1/3 (maybe even 2/3) of the class (bc WashU already selects for such an elite top notch group to begin with), one would definitely get a lot more interviews to great places vs. the same ranked applicant at a local state school. This is reflected in WashU's match lists, where even in Internal Medicine, students are going to top places:
https://residency.wustl.edu/Residencies/WUSMMatch/Pages/Home.aspx