your point might be wrong

the question is how offen it happen? According to the law, the officer has a right to refuse anyone to enter the USA no matter whether he or she has a visa or not. If people are allowed to revalidate their visas according to the revalidation rule. They should let most of them into the USA. We can say it safe. I will land canada. I found some cases for the people from Islasm countries, but non from China. do you know some Chinese have same situation?