BOTH the maxilla and mandible are BONES that are FRACTURED and would go through a biologically similar healing process.
According to a medical website on bone fracture healing, the first thing they point out is:
"Fracture healing involves a complex and sequential set of events....."
https://www.orthobullets.com/basic-science/9009/fracture-healingYour statement posits this complex healing process is 'straight forward' (to you?) when the fracture is to the mandible.
I can't answer your question in the way you present it. What I can do is tell you the following:
1: BOTH the maxilla and mandible are BONES that are FRACTURED and would go through a biologically similar healing process which would be considered a 'complex' one unless someone is really conversant in bone biology.
2. In terms of reducing things so they are more straight forward or 'intuitive' in the absence of being conversant in this complex and sequential set of events that transpire during fracture healing, we would look for more commonalities that relate broken bones to 'fixing' them in place. For example, plates and screws which keep the bones in place while they 'heal' (which can be removed after the bones have stabilized). So, both the maxilla and mandible have in common that they both need to be fixed in place.
3: As to the reason(s) plates and screws are removed later down the line. Sometimes it's because of an infection. Other times it's because they are not needed anymore after they've done their job stabilizing the bone in place. Since bone 'healing' involves osteoblasts (generation of bone), bone can form an overlay to the plates which would make them harder to remove later down the line if they got infected.
4: In the case of a bone 'graft', it's done so that the cut area of the bone(s) have CONTACT with a POROUS material they can INTEGRATE with. If it's a posterior downgraft, it's kind of like a wedge shape as to 'wedge down' the posterior maxilla to affect CCW. Bone 'grows' INTO the pores of the porous material so that the material becomes INTEGRATED with bone.
So, plates and screws are used to FIXATE the bones in place UNTIL they 'heal' or become stabilized in that position so the plates and screws are no longer needed. The posterior down graft also needs to be fixated until bone cells (and/or other cells that go along with bone healing) INTEGRATE with it so that it becomes stable.