Whataboutism doesn’t really apply when pointing out a double standard. It’s true that both places shouldn’t do the bad thing, but it’s more about the individual’s reaction to that thing depending on who does it. The average US citizen will criticise the CCP for doing plenty of the same things their government currently does, or has done in the past, that they support.
Furthermore, it’s important to note that when this kind of thing happens, people treat it as China’s government’s fault, but when Tesla cars explode, people don’t consider that the US government’s fault.
I think what they were specifying was the role GNU plays in that sentence. Personally I don’t like calling one GNU/Linux and the other Linux, but the defining point of GNU is that it’s uses only free open source software, and does not contain any non-free (as in speech, not beer) software.