I think, as a general rule, people involved don't like to discuss legal details, because discussing legal details can lead to potential legal liability. Plus the details are probably complicated and open to interpretation.
Lawyers don't tend to be a chatty bunch.
It's just safer for anyone involved to not discuss details - and people like Feige probably only know the broad strokes.
Based on everything I've read over the past 20 years, I feel reasonably comfortable in approximating the FF deal as this:
Production (principle photography) must begin within 7 years of last film's release or the rights will revert, and the finished film must be broadly distributed within 8.5 years of the last film's release or the rights will revert.
That would mean production of a new film would have to begin by August 7, 2022, and while that may not be exact, I'd bet it's pretty darn close.