From the manual:
'The modifications are done in memory and alter the original files on disk only when the images are saved with the save function'
'The rotation is not saved until you save the rotated image'

Users are familiar with the concept that changes made to documents aren't saved until they tell the app to save.
Does EOG have actions that break this convention, thus requiring the convention to be stated explicitly?
What users should be warned of however is that EOG doesn't give a warning on closing an image with unsaved transformations. Is this a bug?