>>8812183The red one has robot fists inside her wheels for supporting original concept's combination with just the four girls
>>8806764However, they did also request the reviewer of their prototype to skip that mode and "leave it as surprise" for the fans as a "hidden bonus". Could be Chinese double-talk for "it's there but it's ugly", read into that what you will.
The in-depth review with the designers in the background:
https://www.bilibili.com/video/BV1Ft4y1v73ATransformation and combination only:
https://www.bilibili.com/video/BV1ED4y1X7F8 