BUMP!
Straight from the producing horse's mouth:
Because they had all of the letters loaded into the slide projectors for each hexagon, they could have theoretically had any configuration they wanted. When it got close to time to start production, here were the problems that occurred to them with doing this--
Somebody would have to sit down during the week leading up to the next taping and go "Okay, we'll put the R next to the B for game 1...no, wait, we used the R next to the B in the configuration for the previous match...let's see, what letter haven't I used yet on this board?" And that seemed like a lot of work for the thankless task of coming up with a unique jumble of 20 letters for each game of each match.
Once the shows are taping and it's time to start a new game, the person in charge of the game board would have to pull out a paper guide, check which configuration they're using, and then painstakingly go from hexagon to hexagon..."Let's see, #1 has to be on F, #2 has to be on W..." and then double-check the whole thing and make sure no letters are up there twice and that it matched the guide that had been arranged for them. So they were anticipating about a 5-to-10-minute stopdown before each game to do that.
It was much easier to come up with 20 jumbles of letters and arrange the letters in each slide projector to correspond to those jumbles, because with the remote control system they had for the slide projectors, they could say "Set all the slide projectors to position #7 for game 1, then set them to position #18 for game two, and then..." It took one press of a button to do that, and no stopdown would be needed.
And that's the story of why the Blockbusters board used finite configurations.