You are talking about the two different things in the eyes of the IHSAA...pairs vs. site assignments.
The district winners (other than the lowest RPI district champion) get to host a 1st Round game...it does not mean they are the top 8 RPI "seeds".
For example, there is a good possibility that even if Western Christian wins tomorrow night, the top 4 in the RPI will be Van Meter, Western Christian, West Branch, and West Sioux, with DNH finishing in the #5 spot. (And even if you disagree with this and say WS will drop below DNH so the top 4 will all be district champions, let's just agree to disagree on this point for now.)
So West Sioux would be in the Top 4 and thus would HAVE to be in a different pod than VM, WC or WB, even though they are a district runner-up. But even though WS would be assigned to a pod away from the other Top 3 seeds, WS would have to travel to a District Champion even though they would be a lower seed than West Sioux...let's just say Treynor (who would be a lower seeded district champion). And let's just say WS beats Treynor in that 1st round game, then WS would get to host the Quarterfinal game no matter because they would be the highest remaining seed left in their pod what since they finished in the Top 4.
Again...from the IHSAA Post-Season Manual:
SITE ASSIGNMENTS
CLASSES 4-A, 3-A, 2-A, 1-A, A, 8-PLAYER
For the first round games:
- The RPI at the end of week 9 will be used to determine site assignments for first round contests.
- When a district champion plays a district champion, the district champion with the highest RPI will be the home team.
- When a district champion plays an at-large qualifier, the district champion will be the home team.
For the quarterfinal-round games:
- The RPI at the end of week 9 will be used to determine site assignments for quarterfinal round contests.