HD is independent of r.
And it's not the minimal set of vertices that must be visited.. it is the smallest set of which at least one must be visited. Another good explanation of HD is in section 1.3 of the skeleton dimension paper (https://arxiv.org/pdf/1609.00512.pdf).
Oh, sorry, I was vague about the visiting—I meant the set must be visited, i.e. something in it must be visited. I'll take a look at that one too, thanks!
