these should be updated as this is for stretch :) post-install/post-install.xml:32- Under the SysV init system <command>halt</command> had the same effect as <command>poweroff</command>, but with systemd as init system (the default in jessie) their effects are different.
the default since jessie or the default in stretch no idea if these are still valid also for stretch; boot-installer/arm.xml:55- The graphical installer is not enabled on the arm64 &d-i; images for jessie so the serial console is used. boot-installer/arm.xml:108- ... Also USB is not supported in the jessie kernel so installing from a USB stick does not work. ... -- victory no need to CC me :-)