Techtree Requirements is a field all units and abilities have in the object editor.
Prior to the release of 1.32, we could easily assign units to be a requirement item for abilities even though this is a function thats not used by default.
This is because the overall system worked properly and allowed people to take advantage and be creative.
Post 1.32 and well within 1.33 however the system is bugged.
i have prepared 2 videos highlighting the problem.
Here is a test map to help: