I know that Egyptology likes to place everything nicely in little boxes, but the symbolic interpretation of Osiris as the Djed and conferring eternal life, or whatever, is simply a guess. Any one of us could conjure up an equally "educated" but unsubstantiated guess.
Osiris, in the image which you just presented, is not even anthropomorphized. He is either abstract or representational. The Ancient Egyptians could have chosen some other animal to represent Osiris, but they didn't. To say that the four discs have some symbolic meaning is a bit of a stretch, unless you're reading out of the Antiquarian handbook. And the pre Dynastic AEs were not abstract artists to my knowledge.
And Osiris is in Abydos.
Osiris looks very much as though he is the pillar. It is not symbolic, but representational. The lifegiver appears to be an actual object, not a concept.