But what does that change? Major flaw of Wankel engines, apex seals are still there, only now they are fixed in place not on the piston. I think "flipping" the design allows for smaller engine but reliability seems to stay the same. Please correct me if I'm wrong.

I wondered that too and then saw this from tfa:

“ "If you recall the Wankel," says Schkolnik, "they have a triangular rotor inside a peanut-shaped housing. We have the opposite, a peanut-shaped rotor in a tri-lobed housing. So take everything you know about the Wankel and turn it literally inside out. They have a long, skinny, moving combustion chamber, we have a stationary combustion chamber that's nice and round. You can drive it to a high compression, just by making the chamber smaller. And because it's stationary, we can directly inject fuel where the Wankel could not. So those are the two key advantages of the diesel: high compression ratio and direct injection.”

I'm just wondering if there is a strong mathematical link between the two. Like flipping the sign somewhere in the description of the geometry of the Wankel engine results in this.

I did some crude geometric measurement on the geometry based on the video and the chamber doesn't seem to have the shape of an Wankel rotor inverted with respect to a circle.