The cheap Chinese stuff often uses knock-off ICs tho.
They can be fairly difficult to detect, and will work for a short time or under very light loads. But they will be nowhere near the spec of the data sheets.
They might massively overheat, not provide the correct currents or voltages, run at lower speeds. All sorts of corners being cut to turn a $2 IC into a 50¢ IC. Or a 50¢ ic into a 5¢ one

So yeh, might be the same PCB layout inside, it might visually look the same (or very very close) but the parts are likely to be counterfeit.

Of course, it's also probable that name brands might be hit with counterfeit parts inside as well. Hopefully their QA picks that up