UploadWizard form doesn't allow to go through the category tree up and down past entering a known category name. This is a big disadvantage toward Special:Upload form which is fully supported by Hot-Cat. Thus, UploadWizard doesn't allow effective and correct categorization and seduces upladers to use categories as keywords instead to choose the most suitable and most specific category from the category tree.
The fact that Upload Wizard doesn't allow effective categorization is obviously an UploadWizard issue (one of many its serious deficiencies). If UploadWizard will use some better method how to enable to go through the category tree, it needs not to use just HotCat.
Could I elaborate why UploadWizard should be a full-blown quality upload interface and not only a shoddy? I couldn't. But If it shouldn't be, it should not be offered as the default upload interface and shouldn't be promoted at all.