Instead it defaults to the title of the object suffixed by the name of the property - the title of the object in the graph seems redundant when you are creating an object view in Workshop.
I think this is a very valid feature request, I’ve filed this internally to make sure that the workshop team see this!
For now, a possible workaround is to use the more customisable charts from Quiver, and embed this as a dashboard. This might be a bit too complicated for a simple usecase, but if this is a really important requirement then it might be worth doing!