You all seem to be operating on the assumption that the playoffs are still split east/west by design. I do not think this is the case, not since the MVC/MAC went away and districts came to the east side in 2014.
In practice, I agree, it's seemed that east/west split has continued - but I would argue that's been more from necessity and geography than from some kind of formal decision from Boone. I could absolutely see a scenario where a Marshalltown or a Mason City might end up playing a Cedar Rapids or Waterloo/Cedar Falls team in the playoffs. Hypothetically, of course.
I know the other classes don't exactly work like 4A, but I think there was a great chance of seeing Waverly-Shell Rock (an "eastern" team) play Webster City (a "western" team) in the first round this year - had Dallas Center-Grimes taken care of Glenwood in Week 9 to win District 8. That would have meant Harlan could have played a Sioux City area team and allowed the Webster City/WSR match. Didn't happen, since Harlan ended up winning the district and having to play Creston, but ...
Prior to 2014, yes, the playoffs were split east/west by design. I don't think that's mandated any more, it just happens from the teams who qualify. Two years isn't a very large sample size, you know. As to what the IHSAA does in the semis, well ... they're just gonna do what they do. My guess is they'll keep the split out of familiarity and to keep people from complaining too much. But if they set up Kennedy-Valley and Bettendorf-Dowling, well, there's no reason they can't do that.