It's possible that the installer fails to recognize this MacBook as a laptop, and therefore does not install the synaptics driver. The bug must then be reassigned to another package, I would suggest "ubiquity" for a first shot.
I am not sure which mechanism is used nowadays, but can you anyway try:
laptop-detect && echo yes
and see if it returns "yes" ?
It's possible that the installer fails to recognize this MacBook as a laptop, and therefore does not install the synaptics driver. The bug must then be reassigned to another package, I would suggest "ubiquity" for a first shot.
I am not sure which mechanism is used nowadays, but can you anyway try:
laptop-detect && echo yes
and see if it returns "yes" ?