That is absolute nonsense. Both I, and my wife, can attest to foreign students at our respective schools as being the worst examples of cheaters. I even had two foreign friends in my program tell me they had to cheat to be equal with people like me, because I knew English better than they did.
I went to a top school, as did my wife.
We recruited the best of the best at grad level world wide.
That gave us a roughly 50-50 American to foreign student ratio
All of our people were far above average
I was responsible for academic integrity and we did not have cheaters
I personally helped shepherd a good number of foreign PhD students through the H1B program for the reasons the H1B program was originally intended for-to give outstanding foreign students with academic credentials and skills otherwise unavailable a path residency and citizenship so they could contribute their unique skill sets to benefit America
That was long enough ago to prove that virtually all of them went on to become American citizens who have made major positive contributions to America