Below is the type of Chamonix 4x5 I'm familiar with. As you can see, the pivot point is aligned with the bottom of the rear standard frame, not the bottom of the ground glass area. Yours may be different. But the location of the bottom of the frame will change compared to the pivot point depending on whether the back is set for horizontal or vertical.
Either way, I'd still always double-check the focus after changing the movements. Perhaps it's just a matter of personal working style.
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