From what I see, they are using the earliest original recording. For instance, let's look at Team B 3rd's cast
here.
井上奈瑠・浦野一美・多田愛佳・柏木由紀・片山陽加・菊地彩香・佐伯美香・早乙女美樹・田名部生来・仲川遥香・仲谷明香・野口玲菜・平嶋夏海・松岡由紀・米沢瑠美・渡辺麻友
Among the cast members are Inoue Naru and Kikuchi Ayaka. Naru left AKB48 during this stage, and Ayarin was fired a few months prior to that even. No Sasshi credit, either. This is definitely the earliest version recorded.
Also, for B5, Milky is not listed while Oku Manami is, which supports this theory further.
I'm so thrilled these are genuine original recordings. This is REALLY exciting.