Those two printers are also smaller and not as accurate at high speeds. The A1 Mini's slicer automatically places parts close to the Z axis in an attempt to reduce the issues and it uses input shaping, but given the printer can lift itself off the ground at default speeds that's not a perfect solution either.
There's a reason the larger and faster printers often use the CoreXY design instead.
Of course, there's always trade offs in (mechanical) design choices. But their static accuracy absolutely is that good, which is fascinating at that price point.
Yes but they're not robot arms so it's not as fascinating. The length of the arm amplifies error so if you made a "mechanics and steppers" arm with the same positional accuracy as a printer, the motors would have to be much more precise or if you geared them down, the backlash extremely low like an industrial robot arm.
Depends on how much power you need (speed times force, acceleration and deceleration...) and how much stiffness you need (can't bend?).
Also depends on how much travel you need. It is easier to get 50 micron accuracy over a total length of 100 micron compared to a total length of 1 meter.