High spindle speed, low torque and limited rigidity are actually pretty manageable for CNC mills. So long as the endmill sees a consistent and appropriate chip load it's fine. Positioning error (control error, backlash) and spindle runout can massively affect chip load, but rigidity/weight of the machine can be compensated for with light cuts and small tools.
1/32 endmill for hard milling up to 70RC
If the machines are well built and carefully programmed, it should be OK albeit slow for hard materials. That said, they won't be able to do a lot of operations like tapping, boring, reaming, drilling, facing, etc. that inherently require higher torque, lower speeds and better rigidity. And, the small cutters get expensive with pretty limited tool life.
IMO the boldest claims are about the controls. As
@Upnorth mentioned 5 axis ain't easy, especially if you have to baby the toolpaths, need extra precision to handle tiny tools, and market to the knuckle-dragging public. Also, I recommend against any device that requires internet to meaningfully function, especially from startups.