I am 80% sure that the Orkulus can use Debris Vortex to heal from debris that comes from cancelled structures.
I tried to test it but it is quite hard to replicate such a situation, where you have an area with no real debris, full of cancelled structure debris and a damaged orky nearby that can use it to heal itself.
I think I managed to make this 'bug' work, but I am not fully certain that there was no other debris there.
Potentially it could be quite game breaking, since one could plant an orky and build-cancel-build-cancel-x500.000 some trade ports or whatever, potentially giving the orkulus an extra 100.000 free hit points during the next fight.
If someone can replicate it or definately confirm this bug doesn't exist, please do so.
edit. In case you don't know:
- a structure that you cancel before the constructor starts working doesn't leave debris
- a structure that a constructor began making does explode and leave debris.