The same overall exposure (film + print) would not really work because the human eye adjusts for shadows instantly. Film + print do not. The dog in shade probably appears "darker" in the print than it appeared in real life. Keeping global exposure (film + print) constant would work if film + print could mimic human eye + brain vision, but they don't.

In this case it probably worked because in the morning light the contrast is low, there is not so much difference between shade and sun, as there is in the central hours of the day. I suppose it wouldn't work as well during central hours of the day without compensating during printing so as to obtain a tonality which is as the mind recorded and remembers it.

In the morning situation Mark was shooting I would have metered for the shade (expecting something like LV11 or LV12 I suppose) and left it there in manual position leaving the exposure latitude of negative film toward the highlights take care of the details in sun light.

I am surprised by the choice of the north sky as middle grey. Isn't that too bright a reference? I would have used a concrete wall in shade to peg my "shadow" exposure. Using B&W that is basically a "good for all situations" exposure unless the light changes substantially.