I just...I don't know. I dont find Rihanna's sales un-impressive.
Rihanna basically had 1 single the MOTS era, because IILTWY didnt really do anything, and people labeled her as a one hit wonder, so Gold was good.
AGLM era, she basically had a #1 hit and a successful Top 10 hit. Break It Off peaked and plummeted, didnt even go Gold. She sold 1.3 Mill with that, which I think is very impressive.
I understand the GGGB era can be a little iffy, but I still think it sold well.
Rated R also really only had two singles. Russian Roulette peaked and plummeted, and didnt even go platinum, and Rude Boy only hit #1 because of airplay, so platinum was successful.
Now on to Loud she had 2 #1 hits, but she got lucky with them, and they weren't huge digitally, so they really are more like successful Top 3 hits, plus another one, and she is already past platinum.