My guess is this game was in development and they simply ran out of time.
However, one also has to wonder how the production version was so much different than Quicksilver. You'd think if they were trying to rush something out the door they would use the existing Quicksilver code and just change the sounds. Rules are the same, at least according to the apron cards. So why go to all the trouble to either change up the switch matrix in the code or design a different playfield harness?
Unfortunately, we don't know how much time passed between this prototype and and production version. Seems silly to me to already have flyers produced with the Quicksilver playfield when you've got a guy working on a widebody whitewood.
Another interesting thing I noticed, the prototype backglass is dated 1982. The production glass has all the same verbiage, but no date.
The fact that the ROMs are labeled leaves me with hope that the game flips. Being v1.0 it may not be very feature rich, and may not be the final code as the designer envisioned. That's why I want to know if the rules written on the playfield are in the code.