The video and its subsequent response sparked a significant reaction on social media, with numerous users rallying behind Sangwan's statement. However, some others disagreed, asserting that personal opinions should not be shared within classrooms.
It's a thing that every Chinese knows, that the students weren't massacred. They were the main force behind the whole thing, it's not a minor detail. The collective memory, the meaning of the whole thing would be vastly different had they been massacred. It's more or less a symbol and reminder that you'll be "invited for a tea" before anything actually bad happens, that shit is oppressive yes but it's not cultural revolution times where it was nigh impossible to know how you're even supposed to act, where the limits are. They're still fuzzy but they'll be explained to you over a stern cup of tea nowadays.
It may be a small detail from your POV, it isn't from the Chinese one.
It's an euphemism, think similar connotations as "offer you can't refuse". OTOH might involve actual drinking of drinking-temperature tea, it's China after all.
It's intimidation that's for sure. But it's better than being dragged in front of a random assortment of culture revolutionaries to be judged by whatever standard they come up with today.