All good stuff to include in the wording of the complaint as it supports your view that the suction plate on the mount was inadequate/not fit for purpose. To assists in potentially removing your own actions or neglect as a potential source of the failure and points more toward the mount being the problem, causing the damage to the phone.
The wording that you took all reasonable actions to ensure that the mount was fixed to the windscreen properly as you had a new one week old windscreen free of any contaminants or defects likely to impact on the mounts adhesion and followed Samsung's installation instructions. There is also no known additional actions which you could not have undertaken (maybe apart from gluing the mount to the windscreen) to prevent the mount from falling from the windscreen as it was installed correctly and in accordance with the installation instructions.
It is also worth writing that verbal advice from Samsung officer indicate that the device could fall in hot weather, but such information is not included as a warning in the instructions or provided on purchase. You could assume that this may have been the issue if the mount fell off when the car was hot...and as such is evidence that the mount is not fit for use (or to Australia's hot summer conditions).
(It may be worth attaching the new windscreen receipt as proof that the windscreen is in fact new and can be ruled out as a source of the mounts failure.)