I think the problem is that when displaying as text, WB 3.5 and up print the contents of the directory on one big bitmap and display it inside the window. That's why the scrolling of text mode windows is so smooth compared to WB 3.1 for example.
When you're in icon mode, the icons get drawn out as you scroll I think.. then again, I could be wrong about that, maybe they used one large bitmap for the icon mode as well.
You would think this bitmap would be relocatable to fast RAM by FBlit though, unless there's some kind of a "chip mem only" flag for memory that they've set for those bitmaps.
I guess that doesn't help much, but that's my take on your question anyway
