Ford Vedette question

I have a general question concerning the 1949-1954 Ford Vedette.

Initial 1948 press release info showed that the car was initially supposed to use the new 1949 Ford chassis but instead it used a mix of the 1948 and 1949 styles. The differential is that of the 1930s style but without the torque tube and used outboard leaf springs. The frame used the 1948 X-brace that was dropped on 1949 American Fords except convertibles, and the engine seemed to stay the same even for 1954.

Why didn't Ford stick with the initial plans to use the 1949 chassis and why no changes when Ford altered their frames and running gear along the line?

First picture of bare frame is what went into production and stayed unchanged (I believe) from 1949-1954. The other two are what the original intended concept frame would have looked like.

Thanks!

Eric