The goal is to improve clarity and readability, without introducing big design changes. Follows the recent obmat to object_to_world refactor: the similar naming is used, and it is a run-time only rename, meaning, there is no affect on .blend files. This patch does not touch the redundant inversions. Those can be removed in almost (if not all) cases, but it would be the best to do it as a separate change. Differential Revision: https://developer.blender.org/D16367