I'm only 90% sure how this works. Image de-pulication only occurs with the frames in a single Sprite type and all of it's instances. C2 doesn't sadly doesn't use an Image Atlas. Instead all Sprite frames belong to that Sprite. If you have duplicate image frames in different sprites such as
WeaponSpriteA has image Handle
WeaponSpriteB has image Handle
then no de-duplicaition will occur.
However if you have
WeaponSpriteAB has ImageFrames or Animations, 0-Handle, 1-Handle
Then de-duplication will occur as having all the same images in the same Sprite.
Since your saying you have 5 Sprite Objects(ie not instances, but full on separate objects) then yes. There is no de-duplication by design/limitation in the overall c2 architecture.
I would personally feel better if C2 used an ImageAtlas and the Sprite/Frames/Animations referenced the atlas. Then there would be a solid de-duplication across all sprites. In the mean time. You will often hear me saying. Batch your sprite images into less sprite objects based on type and/or layers.