By "identical", can I assume you mean it has the same surface texture (or lack thereof) as GFS, in addition to the same spectral data and other traits? I apologize in advance for asking this, but in exploring paper alternatives I've often found that "identical" means "the same except surface texture".
Thanks!
There is no difference in texture between the papers I mentioned, not on the paper white, not on the printed areas.
I punched 1 cm diameter holes in the samples I have, went outside and compared them outdoors, overcast sky. Each sample had a slight difference in reflectance on the 90 degrees angle due to the paper fiber direction so when I noticed that slight difference I turned one sample 90 degrees and the match became 100%. If you do that with two samples of the same paper you will notice that difference/equality too. The papers are identical for every aspect a user can consider. I can not comment on what happens to their quality in packaging, distribution etc but in my opinion they all come from the same source.
Spectral reflectance of front and backside surfaces have been measured after the Photokina 2014 and showed identical spectral plots.
BTW, if a user does not have the equipment to make custom ICC profiles then check the different profiles (+ media preset recommendations) available from Felix Schoeller, Hahnemühle, Ilford Imaging, etc web pages. If not identical there could be a more compatible one for the user's specific printer.
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htmDecember 2014 update, 700+ inkjet media white spectral plots