The toller photos do not show a complete build. There are a couple showing filled and taped epoxied seams, and then the next photos show the bed liner over it all.
I have seen a couple of his boat builds on the 'fuge, and he does epoxy the insides on his current boats. Those photos may be the first boat.
No Birch plywood. Birch rots when you think about water, let alone get it wet. Any exterior ply would be better than birch.