That no longer functions with iOS 9.02 and iTunes 12.3. Lot of
doublespeak about "app thinning".
The "improved method" would have you either download new and updated apps
to iTunes and then sync to your iDevice or download app updates and purchases
to our iDevice and MANUALLY download updates into your library from iTunes and
enable automatically download purchases in iTunes and hopefully the new purchases
will download.
Either way is a pain with the second method having the added bonus of having to download twice!
If you are displeased with having to do this, send your opinion here:
https://www.apple.com/feedback/itunesapp.html