FrogReaver
The most respectful and polite poster ever
@FrogReaver
That whole thing was made up (well, not made up...it was a Dungeon World game I ran that was transliterated to 5e). Just assume that (a) the dog shouldn't have been Hostile because of x, y, z (make something up that is intuitive at the table) and (b) assume the circumstances of the PCs saving the dog at the encampment before it fled were significantly impactful to the dog and that having a friendly face amidst a recent history of hardship would be sufficiently compelling for the dog (and that this is inferable from a players' perspective). Fill in the blanks as you see fit to get there.
Just figure out fiction where DC 10 is very reasonable for the Animal Handling check and Indifferent Starting Attitude for the dog is sensibly inferred by the players engaging with the fiction.
I'm not sure why you're defending an imaginary GM here?
Because other than changing the roll of a 2 - that GM played the starving traumatized dog exactly as I would have. So it's not so much an imaginary GM - it's me.