Very brilliant idea, and it helps the value of the token grow, I guess they are just learning from the strategies of Binance, because this was the strategy that Binance first used in making their value appreciate, I learnt that what Binance usually do then was to buy back all these tokens, and they just dont buy them to keep, they buy them to burn, so they burn the tokens thereby reducing the supply of the token available in the market and then the demands available will continue to grow the value, and we know that this is the strategy that make the value of a coin grow more, the higher the demand and lesser supply, the more the value will grow. For these companies that have also adopted same strategy, I guess it is very okay provided they will burn the token.
Binance applies creative method and it helps them to maintain and boost the price of BNB. However, I doubt that other exchanges can get same kind of success with same strategy, because that strategy has become a new trend, then when the trend comes to its end, it will be hard for late-joiners to get success. ICOs, IEOs, buy back and burn, they all good games for early comers.