It means that Shaka as Shijo Shogaku in Shakumon was a Buddha having only a temporary appearance, but Shaka as Kuon Jitsujo in Honmon was the Buddha with true appearance and body, preaching Ichinen sanzen of the phenomena in this world.
つまり始成正覚の釈迦仏は迹門として現した仮の仏の姿であるが、久遠実成の釈迦仏こそ本門として本地・本体である真実の仏の姿を現し、事の一念三千を説いた。