Since you asked @texaspg, I went through the actual AAMC list and I guess I never thought about the fact that even though the number of MSTP schools is the minority, they are the larger programs so in fact, MSTP students are the vast majority of MD/PhD students (456/626 or 73%). Therefore, I think the AAMC data is a pretty good proxy for MSTP.
No, I definitely can imagine that being true at most MSTPs - def fits with my program which is not in the top 5.