I believe maintaining the character set (which isn't actually ASCII, but code page <some number>) for the other views is by design. The tile sets are designed for the detailed level, so if you were to apply those to the higher level views they'd just look weird with inappropriate things appearing on the top level as DF uses the same character to indicate different things on the different levels.

However, there is something in the pack that sets up this separation, as I've had versions where the tile set was applied throughout, which takes some getting used to.



Edit: "something" is TwbT. If you change the print mode to a non TwbT one you get the tileset applied throughout.