venting question to coincide with TPT

This fall/winter has brought on some crazy weather this year. In my repairs, questions, consulting, a question of Truss Phenomenon Theory has come up quite often. I have noticed that the better venting the attic has, the more prevalent the cracks are in the corners of the walls and ceiling.

Has anybody else come to this conclusion? or now that its brought up, what doo you think?

Really, the only homes I see with a lot of cracks are the older ones that have had multiple layers of shingles put on them. Seems the weight bearing down on the trusses has the biggest impact. I would think that the type of sheetrock used would also play a role.