Even I didn't hear about those Buy back but really it is very good idea to increase the price of coin in the market. Still, there is huge chance for people who are holding the Binance because this exchange has great future in the coming days.
That makes sense, but only if it happens in the period when they are obliged to buy the BNB again (I believe, every three months ...) because, the higher the price, the richer the exchange itself ... in general, it must be their interest to has a high BNB price, too. BNB volume continues to increase rapidly. So even though it's manipulated to make investors happy, so what. They reach the amount after selling 20 million BNB immediately. The faster they can buy back the BNB, the better.