iPhone/iPad and HomePod play synchronously

Unless I am missing something (and I hope I am!) iPhone/iPad are not AirPlay devices, just controllers so I can't play one single audio source (a song for example) from my iPhone and HomePod (for example) synchronously.

Usage:

• While playing music on iPhone/iPad add a HomePod to play synchronously with the iPhone/iPad.
• Have an iPhone play music as a device (receiver) for AirPlay. Like one would use an Airport Express connected to speakers.

Am I missing a setting to do this? Are there any Apps for iPhone/iPad that can accomplish this?

I am already very familiar with Airfoil for the Mac...no need to explain its functionality.