The thing is, there is no universal definition of pornography. It varies from country to country. In my country, it doesn’t fulfill some of the criteria, in particular because:
It does not depict human genital organs in their sexual functions
It does not solely focus on the technical aspects of sexuality and sexual life, completely detached from the intellectual and personal layers
The more important thing is that the cropped version of the picture (which was used in the research papers) does not fulfill any criteria to be classified as pornography or even as nude art. Some don’t even know that this is only part of a nude photo. I saw this cropped picture in the 90s and was surprised later in the early 2000s by the full version.
I would say more. This is an example where some random nude photo became something more because it became part of science. So it’s rather an example of “deobjectification” because this picture is focused on her face in the hat, and not her reproductive organs.
Regarding objectification, the picture of any kind has nothing to do with women being objectified. Any person may be objectified only by being treated by another person or group of people as an object. For example, a cleaning lady may be objectified by one employer who does not treat her like a living, feeling person, but not by another employer. The same applies to sex workers and any other profession. It is our attitude that determines whether we objectify someone, not the picture of a woman in a hat.