I don't see how it makes any sense as a negotiating tactic. Consider two alternatives:
1. WotC shares the draft of 1.1 and says, "We're deauthorizing 1.0a and you will like it." Third parties say, "This sucks" and leak the document, leading to public backlash against WotC. So WotC says, "Fine, we're still doing 1.1 but we won't deauthorize 1.0a." And third parties say, "Uh, fine."
2. WotC shares the draft of 1.1 and says, "Here's the new license but you can still use 1.0a if you want." Third parties say, "Uh, fine."
Which of those two do you consider the shrewder negotiating tactic?
You forgot the possibility of...
3. WotC shares the draft of 1.1 and says, "We're deauthorizing 1.0a and you will like it." Third parties say, "Oh, okay."
Or
4. WotC shares the draft of 1.1 and says, "We're deauthorizing 1.0a and you will like it." Third parties say, "This sucks" and leak the document, leading to public backlash against WotC. So WotC says, "Fine, we're still doing 1.1 and deauthorizing 1.0a but the money you have to give us will be less." And third parties say, "Well, that still sucks, but it's better than it was, so I guess we have to go along with it because we don't really have a choice in the matter, do we?"
Or
5. WotC shares the draft of 1.1 and says, "We're deauthorizing 1.0a and you will like it." Third parties say, "This sucks" and leak the document, leading to public backlash against WotC. So WotC says, "Fine, we're still doing 1.1 and deauthorizing 1.0a, but if you individual companies want to each negotiate a separate deal with us, we're down with that." And select third parties say, "Uh, fine" and their deals make them happy and that happiness is spread to all the people for whom they directly influence.
And these are only a few of the possible scenarios. But the point is... they never would have known what the other companies and public would have accepted had they not risked the whole "leading to public backlash" thing. But that's more often than not not that much of an issue because all us nerds often have short memories when things we really like end up getting made.
How are all those people who "swore off Star Wars" when the Extended Universe got cancelled I wonder? They still off the train or did they eventually find their way back like everyone expected?