I don't think the OP is saying that scale length alone is responsible for tone/playability. However, it is definitely a large factor in the equation.
"Floppy" is also pretty subjective. I've got some DR Lo-Riders (.130 B) on my 34" Ibanez that don't feel terribly floppy, but if I were to put that same string on a 36", it would be significantly stiffer. Therefore, if I was used to playing those strings on a 36" bass, in comparison, my 34" B would be 'floppy'.
Please re-read the OP.
literally every sentence is about 34" B feeling like a "rubber band" and on a 35" it feels great, to him. Clearly it's the strings, not the basses, AND/OR mind over matter.