It's because Biden is in a most difficult position, partly thanks to our comrade Jianguo and partly of his own making.It just seems petty and caters to a spiritual victory need, not something substantial.
The correct thing for Biden to do back when he took office was to go "American is back, democracy fuck yeah" and then no more. Don't mention China, pretend it doesn't exist, let all the anti-China fever that Trump stirred up die down slowly while quietly talk to China about helping him out ala 2008. China would have listened back then.
But instead what he did was at every meeting he went to he was all "guys China is super powerful now! We have to come together and do something!" For month he keep reminding everyone at every opportunity how China is rising and America's needs to engage it head on. Then at the same time he continued to print insane amount of money (on this he doesn't have a lot of choice). Now with inflating spiralling out of control more than ever he needs China's financial help, yet thanks to his own actions he cannot be seen to be soft on China. Can you imagine he do something as simple as take off Trump tariff against Chinese import? GOP and Trump will immediately be yelling "Beijing Biden!" and how he surrendered and sold out the country and he can kiss the midterm election goodbye.
And so here we are, Biden cannot upset China because he's still hoping China can bail him out, yet he cannot not upset China because it would be political suicide. He has played himself into a corner.
That's why you see him do these petty little "microaggressions" as he tries to walk a fine line between the two. Playing this game requires a tremendous amount of emotional intelligence and a very good understanding of the other guy's culture and sensibilities, and well those are not America's strong points.