Attack from Mars has no lower playfield, is that a stipped down pinball machine as well. ?

Sure, if the originally envisioned AFM with the moving ship was produced as well as the version we all know, then yes, the AFM in existence would have been a stripped down one I guess.

Gottlieb did some stripping down way back (where are they now?) with Black Hole for example - but they didn't remove the lower playfield. They changed the head box to remove the spinning disk and the sound board to a cheaper one. That was done for export markets where the dollar was making the games expensive. Game play was the same, cosmetic and audio changes were made for cost cutting.