Brett
My apologies as I have just been re-reading the thread as I realised that I may have missed some comments. My apologies also to others who I may not have replied to directly.
You are right the kerf is so thin (1.2mm from memory) that the timber pinching the blade is never an issue. The only time it becomes an issue is when you miscalculate how sharp the blade is and are forced to back the blade out of the cut from part way down the log. Then of course you have to place wedges in the kerf to prevent the balde being knocked off the wheels.
In fact Spotted Gum so often has growth spring in it that the board behind the cut will actually rise up. I had one extreme example soon after I first started milling where reaching the end of a cut of a log about four meters in length I glanced back at the board to see it had risen abou 200mm in the air. Not a good piece of timber at all. The rotating of the log will tend to minimise that effect, but not completely eliminate it. It is the advantage of having a bed to give reference, but as others have noted it is an additional operation in the milling process that is very labour intensive for a portable milling operation.
The larger the diameter of the log the less chance there is of growth stress being present. I recall somebody telling me he had cut some ancient bridge timbers and as he cut them they" sprung." If growth stress is there is remains there until cut.
With regards to back sawing and quartersawing with a bandsaw you are correct if you are talking fully quartersawn or fully backsawn. However grain at 45 deg qualifies for quartersawn too. A swing saw blade is particularly good for quartersawing as it can take both types of cut in the same plane.
Regards
Paul