Also in WNMHGB, one of the crew explains to the castaways how the new ships can break the time barrier. Clearly the Big E had a different drive system than the Valiant, and presumably that new drive was the space/time warp.
Actually, that was in The Cage.
"If you need a holodeck to make an interstellar starship on the bleeding edge of the unknown
interesting, something is seriously amiss."
- Straczynski & Zabel