Dash can take advantage of appledoc generated documentation sets by displaying TOC and click to copy. To be able to do so, it requires `--docset--platform-family` value to be `appledoc`. Current documentation set reference doesn't mention this key anymore, so it seems safe to hijack it. If this isn't desired, you can still revert to empty string or whichever value you want by explicitly using the cmd line switch (of course, you can also do it inside project or global settings plist files).
Turns out recent change to better support Dash broke Xcode quick help - Xcode does rely on `DocSetPlatformFamily` info plist key, must be either empty string or one of the valid platforms. To compensate and still support Dash, a custom key was introduced - `DashDocSetFamily`, if its value is `appledoc`, Dash will use optimized rendering.