The definitions of the coordinate terms in SpatialOrientationEnums is as follows:

Coordinate orientation codes have a place-value organization such that an ImageDimension-al sequence of subcodes says both which varies fastest through which varies slowest, but also which end of the frame of reference is considered zero for each of the coordinates. For example, 'RIP' means Right to Left varies fastest, then Inferior to Superior, and Posterior to Anterior varies the slowest.

This is the opposite of the definitions for the DICOM standard:
https://www.slicer.org/wiki/Coordinate_systems

It is interpreted that the preferred way to describe coordinates is in the "TO" direction or the direction of an axes is increasing. See the following DICOM section: C.7.6.2.1.1

ITK is defined as having a LPS coordinate system. However the SpatialOrientation enums and the OrientImageFilters call the RAI coordinates. This is confusing.

UPDATED:

I propose moving itk::OrientImageFilter to the deprecated module. Users can using this filter by simply enabling this module as it will be available until least ITK 7.0 ( unplanned ).

The itk::SpatialOrientationEnums and itk::SpatialOrientationAdapters usage should be discouraged. Usage where appropriate will be marked with "ITK_FUTURE_LEGACY_REMOVE", which provides no clear time frame for removal.

The core improvement is the introduction of the "DICOMOrientation" class which contains enum classes to describe spatial orientation as interpreted from DICOM with ITK having "LPS" coordinate. The DICOMOrientation class include the functionality of the legacy SpatialOrientationAdaptor, but with the addition of interpreting string representations. Additionally, this new class provides compatibly with conversion from the legacy SpatialOrientationEnums.

The DICOMOrientImageFilter from the SimpleITKFilters remote module is introduced to the "filter user" front end api, to clarify the change to the new DICOM based coordinate descriptions.