If you had a 5 meter tall dog master family responsible for giving you food, shelter and keeping you safe from dog-driven cars, you'd be quite good at reading dog expressions too.
Who had bred you to be good at reading their emotions. Dogs not only grew eyebrows that wolves don't have, they literally evolved a new facial muscle [1]. (African wild dogs have a precursor to it. But it's morphologically distinct in dogs.)
I don't think that it's as easy a two-way-street as that makes it seem.
humans developed extraordinary nuanced expression that most other animals cannot get near matching the depth and breadth of primarily because of the role that those expressions play in society itself.
an aardvark never has to put on a front so that their children aren't taken away by CPS. A donkey's livelihood is never reliant on them selling a poorly maintained used car to a sucker. Rhinos don't run for mayor.
BUT when you start considering animals that do seem to have a culture and society -- take for instance bonobos -- you start to see increased depth and breadth of expression and emotional response.
That signals to me that (most) emotions and expression come after the point of them playing a larger role than just familial maintenance. They seem to be largely reinforced by the needs of a growing social network that uses them to determine individual roles and the prioritization of 'maintenance of the group' rather than the individual.
that said, I am sure your example individual would be good at reading the expressive state of the 5 meter tall dog; I just contend that the emotional states of that dog are more simple and straight-forward than his human pet -- although maybe not since these dogs drive cars...
further research is needed on 5m car-driving dogs.
[1] https://www.smithsonianmag.com/smart-news/dogs-have-special-...