Yes, it's true the OOS numbers are very low, since the school is required to accept a certain percentage of IS applicants. This year, about 4300 OOS applicants submitted secondaries and about 200 were offered interviews.
However, those OOSers that I have met and talked to were all very different, and not all of them had "exceptional stats" (myself included). UW is very specific in the types of applicants they are looking for, and it definitely goes beyond whether you're just competitive number wise. Plenty of 33+ MCAT/3.7+ GPAs get rejected every year, even though many of them will go on to interview at top schools.
The school seems to really love those with strong clinical experiences; the more information you can give them in your activities + optional essay to really convey why their program/curriculum aligns with your skills + interests (and give a "holistic view" of who you are), the better your chances of receiving an II (especially if you cannot get IS status).
I'm probably stating the obvious, but this was just what I gathered after my interview last year, haha