Hi, Further information:jessie iso installer ( http://cdimage.debian.org/debian-cd/8.6.0/amd64/iso-dvd/debian-8.6.0-amd64-DVD-1.iso ) works on the same machine.
I tested it myself and it is documented here : https://wiki.debian.org/InstallingDebianOn/Apple/MacBookAir/6-2
So it seems to be a regression in the graphics stack between jessie installer and stretch installer.
Regards, Laurent