I similarly had an awful volunteering experience at a hospital. Basically, their volunteering program not only didn't give the volunteers any sort of real clinical experience, but we (the volunteers) actively took work away from paid employees who had to log all the 'tasks' they completed in order to be in good standing. There was a limited number of tasks and every job completed by a volunteer was one that a paid employee could not get credit for (and it wasn't as though volunteers were helping out in a crazy busy situation...most volunteers did homework until a job came up).
Anyhow, to answer your question, I ended up putting this experience down on my AMCAS to check a box since most of my other volunteering wasn't so directly "medical". I wrote an honest description about what my responsibilities were but I never made a big deal out of it: I never mentioned it in my PS or in my "most meaningful" essays. It's there, I don't know if it helps, but I don't think it hurts. I have prepared a response that I might give at interviews if asked about my volunteering, but both of the interviews I have attended so far have not asked.
My prepared response is basically talking about how, since I had very little patient contact, I did not learn more about the medical profession than I had as a result of growing up with a parent physician. Then I talk about how and why some of my shadowing experiences were much more valuable as a tool to explore the medical profession.