There is a disparity between the text and the imagery.
When originally drafted, the open air portions simply exposed the dome above but there was not a continuous “roof top” area that could be traversed. The entire notion that adventurers could climb up into and move across the open-air portions of the dungeon actually arose when a cunning playtester worked out the geometry of the spherical dome on top of temple complex. We thought that was really cool and made it part of the module.
When the artist Jeff Brown illustrated the dome, his sense of the space led him to conclude that the entry war was accessible. For game play purposes I think it probably plays better if you can only access the open-air portion from 13, 18, 19, 42, and 61.