Why won't stereo files play on IOS devices?

I'm recording messages in stereo on an iMac using QuickTime that coming from a sound board that's connected through the "line In" port on the computer.

When I Play the file back it sounds fine in QuickTime.

I send it to our editor online and they download to their computer and it sounds fine. After editing the file in GarageBand, they play it and it sounds fine but when they upload it to our website, publish it and then test it on an iOS device, the audio is all garbled and unintelligible.

I asked someone about this and they said "IOS devices can't play stereo unless they have a stereo speaker connected".

SO

I'm wondering how itunes sold millions of stereo songs if all those IOS devices can't play them on their mono speaker? right?

Does anyone know why this would happen?

Thanks in advance for any help on this.

DH