Octahedron shape shows head/tail sizes and roll of bone.
None of the other shape type do that.
With other types, we don’t know if a joint correspond to Head or Tail of bone. And we don’t instantly know if bone is rotated compared to previous or next.
That is important when you are creating the rig. People complained about having Transparency Bones option only in Pose mode.
Now, in a recent build, you should find Transparency Bones option in Overlay popover in 3D View header.
There is obviously the idea to decouple Bones display from other objects display.
That is not absurd. The real object is the armature. Bones are just an element of this armature.
But obviously, they are elements that are requiring more visual info than vertices.
Some additional info could be added. Like existing Face Angle, Face Area, Face normals overlays.
This part of bones display will probably continue to evolve in future 2.8 releases.
We could image an overlay to display bone roll values or joint angles.
But at least, you should have a correct display in edit mode.