Yes, I do consider the lack of self-timer to be a mistake. Despite the increased cost, it would have been minimal.
And, yes, that focus point is determined ONLY when the mirror is at rest. Just try putting a tiny thin object, like the thickness of postcard paper, between the lower edge of the mirror and that metal piece that supports the front of the mirror and you will see what I mean when you try to focus. That mirror height is absolutely critical to forward accurate information into the viewfinder. - David Lyga