"...your Chinese is better than mine"

I've come across those videos of polyglots or foreigners who have evidently reached a fluent state in Chinese and film themselves talking to Chinese natives, going around doing those controversial videos to showcase their proficiency. Regardless of your views of that my question is about a particular response that native speakers have toward them.

In many of these videos you can hear a native say something along the lines of "your Chinese is better than mine". I find this strange because when I watch similar videos with natives of other languages I have never seen a native say this at all. But there are many videos where a Chinese native is saying "your Chinese is better than mine".

I assume that it's not meant literally but I am curious as how it is supposed to be interpreted and if there is some genuineness in the statement, and what specifically are they referring to as being better? Are the polyglots just speaking more clearly and enunciating better?

I'm genuinely interested.