It's hardly a secret. Any grad student in America already knows this - about the blatant/incredulous cheating and plagiarism that goes on between Chinese students. But oh no, can't talk about it. 'Coz it's racist y'know.
If you're saying "The academic culture in China is such that cheating and lying is widespread" -- that's not racist.
I'm pretty sure the post you responded to is making the latter claim.
The problem with the parent statement is that it has the typical lack of precision and accuracy of a racist statement.
Two groups can be compared on important values like "honesty" independent of group size. The comparison will look like overlapping normal distributions, usually with substantial overlap. Chinese students were famous for cheating at my school, especially in the pre-med biology track. I witnessed it myself. I also witnessed brilliant, hard-working non-cheating Chinese students in math and physics. Yeah, there's something cultural going on but it's a lot more complicated than "the Chinese are cheaters".
This statement doesn't "blame the culture". In this sentence, culture means "a set of behaviors". The sentence doesn't speculate about why that (speculated) culture exists, and it certainly isn't saying "Chinese culture promotes cheating". Actually, all it's really saying is, "Cheating and lying is widespread in academia in China". That statement is totally compatible with what you wrote.
When having these discussions, it helps to interpret other people's perspectives charitably. Communication is hard. We don't need to make it harder by assuming that everyone who says something that could be interpreted as racism is actually a racist. Plus, I've found that if I interpret other perspectives charitably, I almost always end up closer to understanding what the other person actually meant.
To choose the maximally flamebaity example, i might not like the current Israeli administration's policy towards Palestinians, but that doesn't make me an antisemite, or even anti-Israeli.