Unfortunately it is the Vista Mail feature which can not be skipped. The Vista Mail initially stores email files inside the folders which already have such coded and truncated names, so the Outlook Import Wizard is not changing the folder name, it just importing email files s and the folders names as is.
Folder names (usually longer than 15 characters – including spaces) are truncated and coded in the e-mail Message Store. Since the import process does not interact with the internal database, the compact folder names in the e-mail Message Store are used. Similarly, it appears that the location of the folders when imported using Mail, are taken from their location within the Message Store rather than the location recorded by the e-mail database for the UI in Vista Mail.
Folders with names over a certain length are truncated and coded to make it easier for the database to index it. For long folder names, you can avoid the truncation+coding by initially making the name less than 15 characters. You can then rename it with a longer name (the longer name will not be reflected in the Message Store).