Sorry if it's just me, but i think the installer is a mess on Amiga. I like it's functions, "pretend" and so (even though i have never used them) but the versions make me crazy. If i try to install Mui right after a clean os39 install, the Intermediate user option is gone, and i have to confirm every @$£@$ step of the install.
InstallerNG also screws things up, although i cannot remember what.. MiamiDX maybe..