According to § 19, the floor area may be exceeded by 50% for garages/parking spaces + driveways.
This development plan, however, does not intend to utilize this scope and does not mention any such second floor area number, except for the mentioned exceptions (which do not apply here).
§ 6 allows the construction of garages outside the floor area.
No, outside the buildable areas. This refers to building distance garages, but says nothing about a (not even usual) non-inclusion of the garages, as you would like to interpret it. Unfortunately, a development plan is not a wish concert for creative interpretations.