Some of the doors require the crystal to be anchored in a room next to that door, which works fine initially. They do need the crystal to be present.

If you then move the crystal to another location without having opened the doors, you can still open them later on whenever you want (See in the screenshot, the doors are yellow despite the crystal being far away).

It might be a design decision to have it that way, but it feels weird on top of making some situations easier. Usually you have the original area where the crystal is quite safe with towers, but in the new area where the doors are, the crystal is closer to danger. If I can just have the crystal go back before opening the doors, then the crystal is much safer there and it just doesn't feel as dangerous and exciting, in my opinion.