The first piece of code that could be connected to WoW dated back to 1997, data was found going back to version 1.12 - and even earlier.
What makes you think they have anything earlier than TBC in regards to something substantial enough to recreate the whole game?
We literally have items as far back as launch that had to be redone due to TBC values - most people still believe that the fizzle effect added in TBC is effecting things like Nightfall and Annihilator to give them inaccurate proc rates.
Maelstrom Trinket doesn’t even behave how it did in Vanilla, I don’t even know if someone’s taken the time to test Tidal Charm to see if it has the same issues.
Skull of Impending Doom had TBC behavior and was reverted to Vanilla behavior.
List goes on and on and on, I think it’s a good indicator that they simply don’t have the data you think they do.
Your evidence is based on a developer who may be being misunderstood due to his enthusiasm over the project.
All evidence that’s actually happening in game says otherwise, no?