I remember the original Voyager "Bible." Tuvok was an elderly Vulcan who was a mentor to B'Elanna. The EMH was named "Doc Zimmerman." And we weren't allowed to mention what kind of animal Chakotay's spirit guide was because that hadn't been decided yet.
Clearly, everything was set in stone from Day One.
Similarly, the original DS9 "Bible" contained no mention of the Dominion, Founders, Changelings, Vortas, pagh-wraiths, Jem Hadar, or any hint of Odo's origins. All of that came later.