The 2 clocks had to be electronically tied together to display the same thing. Or just programmed to start at the same time, even if they weren't directly tied to one another. I imagine the reason the one offstage was eggcrate is because it provided its own light source. "Vane" displays are flat white mechanical pieces you shine light at (like Family Feud's board being flat yellow disks).
This also recalls latter day (Nickelodeon) Double Dare episodes where the supered clock was different from the one behind Marc Summers, and sometimes they'd be out of sync, with Marc reminding us the music is timed to exactly 15/20/30/60 seconds, etc. etc.
When this thread said LEAPS in technology, my mind immediately went to the entire floor being a gameboard on Monopoly Millionaires Club. We haven't quite seen that used to full effect in America yet, as far as I can remember, although Jimmy Kimmel's Millionaire is making great use of it as their set floor. The overseas show 5 Gold Rings is a great example of what we could be doing.
-Jason