The reason this works is happenstance, but it's interesting to see why it still works.
Phong shading is three techniques in one
With phong shading, we have three terms: specular, diffuse, and ambient; these three terms represent the three techniques used in phong shading.
None of these terms strictly require a vector space; you can make phong shading work in world, local, or camera spaces as long as you are consistant. Eye space is usually used for lighting, as it is easier to work with and the conversions are simple.
But what if you are at origin? Now you are multiplying by zero; it's easy to see that there's no difference between any of the vector spaces at origin. By coincidence, at origin, it doesn't matter what vector space you are in; it'll work.
vec3 h = normalize(lightDirCameraCoords - vertexPosLocalCoords);
Notice that it's basically subtracting 0; this is the only time local is used, and it's used in the one place that it can do the least damage. Since the object is at origin, all it's vertices should be at or very close to origin as well. At origin, the approximation is exact; all vector spaces converge. Very close to origin, it's very close to exact; even if we used exact reals, it'd be a very small divergence, but we don't use exact reals, we use floats, compounding the issue.
Basically, you got lucky; this wouldn't work if the object wasn't at origin. Try moving it and see!
Also, you aren't using Phong shading; you are using Blinn-Phong shading (that's the name for the replacement of reflect() with a half vector, just for reference).