It seems like some of us still have very different opinions about how this handoff structure should and shouldn't be used, which I really think need to be worked out and then codified in the spec before we can call the document final, because otherwise no firmware project can trust that it is safe to adopt this. My understanding was that this is supposed to be a universal handoff structure that's free to be used by any open source firmware project for any of its internal purposes at any stage of the boot flow as a standalone solution that doesn't force them to pull in dependencies to any other format. If that is the case then I think the spec should reflect this very clearly and should particularly not contain any language about deferring certain types of data to other handoff structures wrapped in the TL. It needs to be clear that projects will be allowed to freely register tags for their needs without the risk of suddenly getting told by the maintainers that they need to use an FDT for this or that instead.
On the other hand, if this is just supposed to be an early boot flow extension to FDTs, then that's very different from what I understood the goal to be and then I think the text of the spec should be honest about that front and center. In that case, I wouldn't expect much adoption beyond the ecosystem that's already deeply tied to FDT to begin with, though, and that would be far from "universal".