I recently had my 1940's cottage sided with 3/4" white cedar lap siding (no taper) over Keene "DryWall" 3/8" rainscreen mat, which in turn is over housewrap. This type of siding & rainscreen was a first for my contractor but he seemed to enjoy the challenge & working with thick boards & fat trim pieces. He suggests not caulking the ends where the siding abuts the corner posts & window trim. His reasoning is that the breathable mat underneath gives the water a channel to escape, so caulk isn't necessary. Finish will be a penetrating oil (Sikkens SRD). This is a lakefront cottage in northern Michigan so weather can be harsh.

What do you guys think about this line of reason? Naturally I want to believe since it takes a LOT of caulk to seal up all the edges. I'm just a little worried because "everyone else" has miles of caulk.
In-process, showing layers: