As Delfi-C3 goes over the earths poles, it flips itself 180 degrees in Z axis

Are you saying it has an active attitude control ... Or is the satellite rotating with a period equal to that of its orbit?

Actually it is two rotations per orbit. To people on Earth it is "horizontal" over the equator and vertical over the poles and does a full revolution over half an orbit.

A benefit is that it prevents any side from facing the sun for more than 12 minutes at a time... and also lets you plan on antenna orientation everywhere.

Bob, WB4APR