Well we know this tech works because there are already ultrasonic cutters in medical and industrial equipment. So it’s more about whether they implemented it well, rather than some new fundamental discovery.
And for home use: https://www.amazon.com/dp/B0FK9SB5KR
HOZO NeoBlade Wireless Ultrasonic Cutter
I got a wired (usb-c) ultrasonic cutter for around $100 (not this one), and it's amazing for cutting precise holes on electronic project boxes (plastic / abs).
Is it realistic to have enough power in such a small form factor for this effect?
Yes think of it as a more powerful electric toothbrush. There are actually already toothbrush sized ultrasonic knives you can buy online. This just applies the same tech to what largely looks like a normal chefs knife.
“This has all the hallmarks of a product that’s going to be disappointing but I’m so optimistic it won’t be.”
I’m seriously hopefuls it works because vibroblades (I mean, “progressive knives” and “high frequency blade”) are awesome and the timelines of Neon Genesis Evangelion and Metal Gear are getting closer. Which may, or may not be a good thing.