Was it just me or did Saki purposely change back into her +/-0 style both times when she gave Himematsu the win? The anime showed her hand being compatible to the 6-bamboo tile she discarded (called on by Suehara), but she didn't decide to win with it. Not sure about the time that Himematsu ended Iwato's streak, but it seemed to be a similar situation of purposely letting her call/win.
She said it herself that she at first tried to play with the "I have only 1000 points" mindset, but she had to return to her old +/-0 play style pretty soon. It was Kyouko that disrupted the first style by calling a pon in the first hand, changing the drawing order such that Kasumi got the 3p that Saki needed for a rinshan tsumo. And then she lost points due to Kyouko's fast wins. After that she was in full +/-0 mode. And yes, Saki discarded the 8 sou such that someone (Kyouko) could call it (as remarked by the Eisui players). We didn't know it for the 6 sou discarded after a kan from the manga alone, but the anime showed us her hand, and she could have used it.