What Calam said.
In the end, it's down to whether you choose to believe that Cyan is benevolent or malevolent in this context. If benevolent, then there is some reason beyond their control why they must continue to restrict discussion of tinkering (to use a non-inflammatory word) with Uru:CC. If malevolent, then they're just doing it because they hate you and want to make you crazy.

Nobody will change anybody's mind either way. The sense of grievance is too deeply rooted now to go away.
For myself, given the grief they're getting over this, I choose to believe that the reason is both beyond their control and something about which they cannot talk, even to the point of saying that there is a reason beyond "because we say so." Otherwise it would be the easiest thing in the world for them to say so and (hopefully) end this particular rhubarb. Since Ubi is the only other entity involved rights-wise in Uru:CC as far as I know, it would seem that the putative reason is something to do with Ubi. Beyond that I could only speculate, and as Calam said, that's a waste of time and pixels.