Pearl 2 with video file background in layout. Warning message. In firmware 4.20.0

Could someone from Epiphan expand on what this message means?
My project is running entirely progressive from input to output and the media file is also progressive.

“…contains a non-interleaved media stream, issues with audio may occur”

Where and why are we likely to experience audio issues and what are they?

Most importantly, how do we avoid them.