I have long used the iOS Remote app to play music on my iMac, streaming to one of my AirPlay-compatible devices. It’s convenient, and allows me to control the music and the volume with any iOS device.
But since the recent update to the Remote app, it no longer updates metadata in iTunes. Previously, it would update the play count and the last played date, useful notably because this would put music you played via that app in the Recently Played playlist. It’s a bit annoying; imagine if you play music on shuffle, and you want to go back and check out some of the songs you heard, because you don’t recall exactly what they are. Previously, the Recently Played playlist would show you this; now, there’s nothing.
However, what you can do is start playing the music in iTunes, then, later, if you wish, control if from the Remote app. You can skip tracks and change volume, but you can’t start playing something different; if you do, then the metadata won’t be updated.
I don’t know why Apple has made this change. It doesn’t make things better in any way, and only removes useful data from your iTunes library.