Why are Appledoc references to input parameter classes not being highlighted?

Apple documentation has cross reference for input parameters. You can see that NSStringEncoding and NSError are highlighted:

But when I use appledoc, there are no cross reference at all:

This is my config file:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>--company-id</key>
    <string>com.vk</string>
    <key>--create-docset</key>
    <false/>
    <key>--create-html</key>
    <true/>
    <key>--ignore</key>
    <array>
        <string>ThirdParty</string>
        <string>Libraries</string>
        <string>Frameworks</string>
        <string>Testing</string>
    </array>
    <key>--install-docset</key>
    <false/>
    <key>--docset-platform-family</key>
    <string>iphoneos</string>
    <key>--output</key>
    <string>docs</string>
    <key>--project-company</key>
    <string>VK.com</string>
    <key>--project-name</key>
    <string>VK iOS SDK</string>
    <key>--keep-undocumented-objects</key>
    <true/>
    <key>--keep-undocumented-members</key>
    <true/>
    <key>--warn-undocumented-object</key>
    <false/>
    <key>--warn-undocumented-member</key>
    <false/>
    <key>--warn-empty-description</key>
    <true/>
    <key>--warn-missing-arg</key>
    <true/>
    <key>--warn-unknown-directive</key>
    <true/>
    <key>--logformat</key>
    <string>xcode</string>
    <key>--exit-threshold</key>
    <integer>2</integer>
</dict>
</plist>

What's wrong?

appledoc is not developed by Apple; it's an open source project by tomaz. It just mimics Apple's docs appearance. So this is normal that all the features of Apple's docs are not available in appledoc.

The cross reference feature you are mentioning is indeed not implemented.