Press release is from June 6, 2012.
Right before the receivers were released.
Look at the link I posted above.
Apple’s AirPlay1, DLNA 1.5 and Bluetooth® connectivity are built into both models for wireless access and connection, with the ability to play high resolution FLAC and WAV music files of up to 192kHz/24-Bits. Both receivers offer endless music entertainment with vTuner®, PANDORA® Internet radio and access to subscription-based SiriusXM® Radio. Pioneer’s Air Jam App2, available at no charge from the Apple App Store on iPhone®, iPad®, and iPod touch® or the iTunes® store, at www.apple.com/iTunes/
, allows connection to personal sources with its ability to pair up to four devices simultaneously via Bluetooth and create group playlists (optional AS-BT200 Bluetooth adapter required).High Resolution Music Playback – The SC-1222 offers DSD (SACD DFF Files) music file playback via the front USB connection
and the SC-1522 offers the 192kHz/32-bit asynchronous USB DAC for ultra-high quality music file playback from a USB3-connected PC or Mac.
MHL-Compatibility Device Connectivity – The SC-1522 features a front Mobile High Definition Link (MHL) connection for compatible smartphones as additional sources for audio and video entertainment. The front-panel HDMI/MHL terminal delivers content with up to 1080p video and 7.1-channel HD audio resolution."
It would seem then that for the SC-1522 you have to connect a PC but for the SC-1222 you can just plug in a USB stick.