You should ask him if the risk of resorption is really high with iliac crest bone, and if it causes bone erosion and then tell us what he said. I think the risk of infection is relatively low.
I did not invent that, on the contrary, these are scientific facts.
Otherwise, many more surgeons would use iliac crest bone instead of medpor or silicone as augmentation material.
Science has it that SURFACE CONTACT is needed to the exposed CUT surface of the bone. So, if the slice of iliac crest bone has 2 EXPOSED surface cuts, it needs to make direct contact, usually as a BONE BUTTRESS between the mandible which also has 2 exposed cut surfaces from being cut. Basically, any exposed bone cut, if left exposed will tend to resorb which is why SURFACE CONTACT with something else is needed to reduce chances of resorption.
If the harvest SLICE has only ONE exposed surface cut to it, that's the part which needs to make direct bone contact. The INTACT part of it doesn't.
It's highly unlikely, the doctor left any exposed surface cut on 'top' of the cheek bone (because he too would know the science of this). It's more likely that the part left on 'top' of the cheek bone was the INTACT surface of the iliac spine.
By the way, I'm not deferring to anything a Swiss surgeon told me, NOR any affinity to Dr. Z. I'm deferring to my degree in science from MIT.