[CosmoK]

"Perhaps Moser bought the pictures of Nini from Flodqvist but put his own name on the credit in Sweet Little 16--maybe at additional cost?"

I think you are also guessing well about that, since I can at least testify that in Moser's magazines, every pictorials by Serge Jacques (and aliases) are credited to Sascha Alexander. And from what I can remember, Alexander's name is in fact credited on almost every photographs...
Perhaps he had the right to do so because he bought the necessary copyrights to put his name on it, in the same way as MeyerPress, Blumebild and other agencies did at the same period?

Anyway, thanks for your excellent work of investigation!