KAATSU is meant and designed to be used on two arms or two legs at a time, but not on all four limbs at once.
When KAATSU compressions begin, the limbs become engorged with blood. This means a higher volume of blood than normal is being held in the limbs.The body’s circulatory system is a closed loop, so when you have more blood in one area, there is less in other areas, notably, in the core. If a person were to use KAATSU on all four limbs at the same time, the drop in blood volume in the core would be more pronounced. People who are dehydrated or otherwise unwell may find themselves becoming lightheaded, and it could also be possible for them to faint and fall.
Using all four AirBands at once is not recommended. This is due to safety concerns. It is a feature, not a bug.