Okay. The reason for this is that categories are no longer added by BB-Code in VaultWiki 4. What you are seeing now is the category prefix tag parsing as links.
The importer is supposed to detect the old category tags and convert them to appropriate database entries, if the Legacy Category tag option is set correctly. The default setting is sufficient for most imports, but I see you have a CAT tag instead of the default CATEGORY value. While this can be changed manually, the importer should be able to get the old name of the category tag itself. This was not working properly, so no category tags were detected during the import. I have updated the code that converts tags in the hopes of catching this case for next time. Unfortunately I don't have a test VaultWiki 3 database I can really try it on without spending a few hours making new test boards and filling them with wiki posts.