Why does IfcRigidOperation support IfcPlaneAngleMeasure

The usecase of IfcRigidOperation is to do a simple **translation** from A to B, most commonly when you truncate large coordinates.

Yet FirstCoordinate and SecondCoordinate allow IfcPlaneAngleMeasure... but why? Lat longs (i.e. angle measures) are very small numbers anyway which seem as though you'd never need to transform them, and the usage of another unit type complicates matters (default unit of angle measures ... radians / degrees?) and mixing of unit types between object placements which are IfcLengthMeasure + IfcPlaneAngleMeasure = ?

I'm a little surprised and confused on how to implement this. It looks as though it'll just create a lot of confusion for users.