I imagine there would be no contact with the engine wall, just a narrow gap with an active system to adjust the size of the gap, similar to some jet turbines. The video goes into it a little bit at this time:
And someone in the comments who has experience with building this kind of engine talks a little about how its difficult but not impossible to lubricate the seal with a higher viscosity fluid that will want to build up and prevent a vane from fully extending at high RPM. A different comment points out that piston rings experience similar problems with carbon and grit.
Exactly what time, the link you added just sends me to the beginning and I didn't want to watch it all the way through again lol
Piston rings don't have to move under their own force though. You can start up the engine and it'll break loose. The vanes use a spring, if it's jammed up enough to oppose the spring then you have to take the engine out/apart to fix the problem. I'm not sure what other problems might arise from not fixing that issue in time.
I'm kinda inclined to agree with the other commenter, it feels like a design that has even more performance benefits than the wankel, but also seems like itd be even more prone to the same reliability maintenance and emissions issues that wankels already have... Which already aren't considered particularly practical