Synthetic oil use on flat tappet cam after break in

Used Joe Gibbs mineral based for break in first motor 318 solid flat tappet, 2nd engine stroker solid roller both engines put around 5k miles than have switched to full synthetic Penrite with Zinc 15-40. I always inspect oil on change 3000 mile spotless no signs of any metal. When I removed sump to change a bad remain went with a better quality seal anyhow inspected main bearings while the sump was off and checked cam lobes no signs of any wear or marks I was quite impressed on how spotless everything was cylinders still had the cross hatch .