If you have a single eye on all 4 side, you can see a field of view of 95 degree of all 4 sides, you are missing 85 degrees from each side, hence it is not omnidirectional.
Even with 2 eyes, our vision on a single plane is not 180 degree, it's 170 degrees, which mean there are roughly 10% of your eyes cannot see. In fact, even with 3 or 4 or 5 eyes, you cannot never achieve 180-degree vision on a single plane. That's some principal regarding stereoscopic vision I forgot the name.
So no, even if you stack the entire side of a KJ-500 with sensor, the sensor cannot pick up a certain degree depends on the field of transmission of that antenna. Like human eyes, anything with an arc will not achieve true omnidirectional.
And with 1 sensor, depends on that sensor antenna field of view. Say if that side sensor is 120 degrees side to side and 90 degrees up and down, then you will have 60 degrees on both sides and 90 degrees on elevation they cannot see.