That's right. There is no foam under the board (PCB). My personal guess is that without foam on the bottom, 4 attachment points provide good insulation of the plate and board (PCB). And the sound is better. And if you put stock foam from the box or custom foam from a custom board on the bottom, then the plate transmits vibrations more strongly to the case. The thickness of the walls of the top case (top part) is too thin. The body out of the box has resonance and a walking sound. Yes, logically it should be the other way around. Foam on the bottom should remove this sound. BUT, no matter how I tried, the best sound - without foam on the bottom. Plus the flex is good.

If without color. They are very similar. Their sound is very high. This is not a PBT sound, but a high-pitched sound similar to ABS. Same price. almost the same basic set and support for form factors.