> Many of the 6x6 poles
> appear to be squared-off single trees, while the end grain of the 2x6's gives the impression they were >cut from larger diameter logs.
As a part-time sawmill operator, I can add this: If you want to saw a 6x6, you plan it to be the center of the tree, so it has the heart in the center, and stands a good chance of staying straight. To get to it, you may cut many 2x6s off the outside first. The heartwood near the center is the best part of the log, because the younger growth wood around the outside is less dense. Some of the 2x6s you cut will be young growth, others will be into the heartwood.
As far as these laminated posts, I would think that wood species, grain direction, fastener selection and application, and wood moisture at time of assembly, would all be important and potentially unpredictable factors in the final product. I can see how they could save you money though. My 18 footer 6x6 were $50 apiece.