To plane the timber or not to plane them depends on the frame's intended use. If it's a barn or outbuilding that's one thing, if it's a house frame it's another.
When I was at Steve's school, a student asked why was he building with all planed timbers. He response was that after building many houses in Maine over the years, all with rough sawn timbers, he'd talk to the people who lived in them. Many of the housewives would complain that the rough sawn timbers looked dusty, no matter how they vacuumed the timbers the pores of the timber seem to appear to be holding dust. And they didn't like that.
Planed timbers are much smoother and don't have the rough surface to hold the dust.
This is why he changed to all planed timbers.