I was an undergraduate at UCSD, where Haiyu did his undergrad. He TA'ed our honors analysis class the 2018-2019 school year as an undergraduate TA. Like the below comments say, he was arrogant and unhelpful even back then, and certainly did not present a welcoming attitude to his students.

is he a good TA? maybe
can he grade things? yes, as good as a compiler that doesnt even accommodate the slightest error

The old reviews are outdated. Haiyu is a great TA. He is super helpful and knowledgeable.

Old reviews are not accurate. Haiyu was a great TA, always clearly puts effort into teaching during section and office hours. Clearly knowledgable about the subject, kind to students. Maybe a tough grader but homework grades don't really matter for this class anyways so having more critisism is helpful to iron out issues before tests, which make up most the grade. You can not do any homework and still get an A theoretically (you won't).