This is the most ridiculous claim that I have heard of. China's military doesn't have any business deals with the US. US imposing sanctions on General Li is just useless and for nothing.
Beside, there are a ton of Chinese politicians got sanctioned by the US. None of them got striped of their title. Whatever happened, it has to do with internal corruption or espionage. In addition, General Li got the promoted when he already got sanctioned by the US. Nobody important gives a damn about the US sanctions anymore.
Well if we ever get such information it's just guess work for now.