That's true, you could do it that way too

However, I suspect that with such an arrangement your design should probably reflect such an offset, otherwise accuracy is going to be about impossible.

Like I said in an earlier post, I was kind of oversimplifying at the first. The only rule you can really set down is be consistent. I think that if you view the lines as lines of balance than positioning will be easy.

Also another thing, if lines mark centers how do you use a plumb bob to align timbers with marks on the ground? To me it just makes sense for that reason to have edges align.

But I should say this regarding alignment -If you find a system that works for you, by all means use it and please tell me about it too!