In a similar way as Roel, you are using the striking characteristics of the lens to create an image and not simply to show them off. Here you are showing the shallow depth of field and unusual characteristics of a vintage lens to illustrate a vintage lens with similar characteristics. The composition works and the barely discernable face adds welcome mystery.
You mention you sometimes doubt whether your efforts at documentation of such lenses are worthwhile, but you also use the word passion, and as long as you enjoy it then it is definitely worthwhile. Maybe the topic is niche, but that it is exactly why it is worth doing. An article about Canon lenses, for instance, would not be as important, since there is so much accessible knowledge already. I had a quick look myself and read an article with interest, which I picked pretty much at random. I also enjoy your images, as they illustrate by using the lens to create a piece of art, rather than a test chart or a straight forward "here-is-a-flower" illustration of its capabilities.