The faces a dog makes, or their displays of expression can intimidate some people, while cause others to smile and melt with warmth. Maybe fond memories are triggered, or they simply just read into the expression differently. It all depends on who is on the receiving end of the expression, don't you think?
Now this face makes me smile every time. Cleo looks grouchy when I think she just had something stuck in her gums or she had cotton mouth. But if you didn't know her, and saw her do in this person, with 85 pound of girth backing it up, you might think this was a scowl.