Yes You are Correct, for example, the Isle Of Peace will let you visit the past once you have completed a certain amount of tasks ie: 3 temples which will all give you an ordinary key that is used to open 3 locked doors inside the remains of the old Hyrule Tower in the castle which will bring you to the past, and you will be in a full land marked version of Hyrule without all the water.
PS: I use the PURE ZC tileset.