I would guess that WotC includes a blanket "You can never publicly discuss anything about this deal for all eternity" clause in all their contracts. For example, their lincensing arrangement with Gale Force Nine ended at some point in the past year or so—quietly, with absolutely no comment from GF9. Granted, in the case of GF9 the muzzling may have been instituted as part of their lawsuit settlement wit WotC. But I suspect it's simply S.O.P. for WotC, given what we all know about how the company seeks to use the legal system to create a cover of secrecy under which to conceal their shady business practices.