Submitter here: I have the same excitement (though not a sailor myself, just a spectator). I actually wondered about a kite pulling a boat a while ago myself, and now someone goes and does it.
I was surprised how fast the foiling technology has been spreading after the America's Cup. There were the foiling moths (small sailboats) before, but now it seems to be more popular. Then recently, I saw something about kiteboarders fitting a foil to their boards and gaining speed. Now this.
One disadvantage of the kiteboat is that it requires a bigger sail and thus longer lines. That will increase the risks of entanglement in a race. And with 80-meter lines, this prototype already has to worry about bridge clearance on the bay.
The combination of kite power and a foiling hull make for crazy speed. 31 knots on a relatively small craft, in 10-18 knots of breeze is incredible, and must be a huge rush to drive.
As a racing sailor, I'd be interested to see how these boats could compete in a fleet race setting, or even a match race / America's Cup style setting. The more of these types of craft I see, the more I am hoping my kids will be sailing cheap foiling kite dinghies at 20 knots in the next 5 years. Exciting stuff!