I don't entirely disagree with you, believe me, but that is the way its heading. But, checking does show the direction of the true "grain" of a piece of wood. When you split that piece of checked firewood I can about guarantee it will cleave in the plane of the check, that is how the timber will fail. If you see a diagonal check across a timber, measure the slope of that check and use that as the slope of grain in determining the allowable stresses that the engineer will use in determining the timber"s strength. These are sympathetic jobs not an either or, a good grading gives the engineer what he needs to design safely.
As far as whether to trust the TPI grader, or the engineer... I'd rather you were trained and approved to gradestamp your own
At the end of the day, after you have worked the timber, that is the true grade. You are ultimately the grader no matter what the timber was to begin with. If the engineer assumed a #2 strength and you gave him a timber with #3 sloped checks, the timber is weaker than designed. A mortise across from a knot could weaken the timber more than intended, or not, knowing the allowables lets you keep the strength up to the engineer's assumptions. I attended TPI's grader training class, and feel I did bring more to the table than many of the "real" graders that are on the line stamping what I cull around at the sawbench every day. I can't change that, the training did give me a better eye, I learned alot. I think it is worthwhile for a woodworker to know the rules and the whys. Being well trained as a group might help when your local enforcement of these codes tightens.
