It is known that, the solid element like C3D8R do not have rotational degree, namely UR1, UR2 and UR3, but this kind of element do have translational degree, so we can not define any rotational bundary constraints to this kind of element, but we can define a Reference Point and use the coupling option to couple the reference point and the boundary of a model constructed using soild element like C3D8R and add rotational bundary constraints to the reference point. How can you explain this?

Abaqus ​​​​​​​