It is a feature included in VP9 that wasn't in VP8. It's to do with the EX1/EX3's MP4 container with mpeg2 needs to be rewrapped in MXF. Not personally having the camera, I'm sure you understand this?
The files copied by V9 can be used in V8, they just need to be rewrapped using the Clipbrowser. The result of doing the rewrap might not be the same as what you get with V9.
The EX cameras break long recordings into chunks. The rewrap to MXF joins the chunks. V9 doesn't do any joining so a long recording ends up as several events on the T/L.