What we do know is that there are newer papers from the same researcher. The lead author, J.R. Reel, is actually the author of the second paper I linked to here.
First, looking at progestational transcriptional activity, they found that nandrolone "at 10–8 M, increased transcriptional activity to the same extent as the progestin standard, R5020, at 10–8 M." Second, they performed a functional reporter assay and looked at alkaline phosphatase activity, which is produced in response to progestins in T47DCO cells. At 10-8 M, nandrolone "produced substantial increases in alkaline phosphatase activity." The conclusion states that "as we have shown here, 19-norandrogens exhibit considerable progestational activity both in vitro and in vivo."