This isn't the metric you are looking for, but I believe the basis of this argument hinges on the proposition that financial need for medical expenses varies from demographic to demographic. I believe this is trivially demonstrated (statistically and from a common-sense standpoint) by looking at different age segments. Older people (baby boomers come to mind now) certainly do need more healthcare than younger people as a product of aging. Citation from 2008: http://economix.blogs.nytimes.com/2008/12/05/why-does-us-hea...
Does that mean they would deserve a greater financial allowance? That is for the person designing the policy to decide; the article suggests no. I offer no opinion on this.
My main question is ... having read the article, I don't actually see the libertarian argument here at all. It seems to say it is simply "more libertarian" than what we currently have (with supporting arguments like "smaller government", "cheaper overhead", etc.) - but ultimately, the spirit of this proposal doesn't seem to be in line with these values at all.