Hi Res from iPhone vs AppleTV sound

Not well versed in digital music.
 

I’m retiring my iPhone 7+ and thought I’d get a camera connection kit and usb cable and run the phone as a high res playback direct to my DAC.

it’s running into a Schiit Modeus.

My AppleTV doesn’t do hi res, but the signal goes via HDMI to my tv which passes the audio to Optical out and into the optical input on the Modeus.

I was A/B’ing then and the hi res via usb is noticeably thinner whereas the ATV. Is full.

Maybe there’s more to it?