In that first link the guy must be sending the video up via USB into the unit. Normally VIM is to allow you to do the illegal activity of watching video whilst driving playing it off the SD card. Normally video is shut off once the car reaches speeds where to door auto lock / reversing camera reverts etc. Japan you see drivers, driving around watching TV. In Obdeleven the bit of text "Video//MirrorLink//SMS option" probably unlocks mirror link as well. Mib2 did have mirror link in it then it was taken away or something link that. This is a VW that it is being done on but one can assume it works the same since its all firmware but slightly tailored to the sub brand.... or the action of VIM does the trick. Possibly the Obdeleven VIM trick enables mirror link as a suppressed menu which mib2s have. Hence the reboot of the unit after the mod.
Probably you need to do a few Google's to see whether VIM on a Seat using a different coding device does the trick. Clearly on that link they have their Android car engineering apps displayed on the 5f unit. The non Obdeleven Pro way of doing via coding not via one click will have been published so you can eyeball that to see which settings they change. The one click app developers will have implemented that.
As I said I recall some people were hacking AA itself to free it up from the constraints of the built in apps. Using AA which is the other way if the link above uses a feature that didn't get implemented in Seat units.
Another link for you
Not every Android Auto app is available on Google Play. Here's how you can install unapproved apps without needing root access!
www.xda-developers.com