Right now, Chromecast devices do not support updating metadata during playback, so this information can only be updated when a track stops or starts.
In order to support gapless playback, Roon sends audio to Chromecast devices (and other protocols) as a continuous audio stream, so there are no track boundaries at which we could update the information displayed. Unfortunately, there’s no way Roon could send this information and keep it up to date on these devices while also supporting gapless playback to Chromecast devices.
If Google implements a change here, we can definitely revisit this. For now, note that it is possible to use one of Google’s Chromecast devices on your TV (in conjunction with playback from the Sony AVR) to display track metadata, lyrics, artist photos, and more on your TV.