There's no end to arguing with someone who claims they don't understand something, they could always just keep repeating "nevertheless I don't understand it"... You could keep shifting the goalposts for "real understanding" until one is required to hold the effects of every training iteration on every single parameter in their minds simultaneously. Obviously "we" understand some things (both low level and high level) to varying degrees and don't understand some others. To claim there is nothing left to know is silly but to claim that nothing is understood about high-level emergence is silly as well.