First of all, since you're new to the forum, you may not know but SCMP is regarded (by everyone, not just pro-Chinese members) as a highly unreliable source full of fake military "experts" like Andrei Chang, etc...
Secondly, this is again, maybe due to your ignorance of submarine operations, an example of you believing whatever you read because the paper claimed that some "expert" said something. Since developing a filter requires some knowledge on the subject, you don't have one. There are "experts" that say anything. Some say the Chinese economy will collapse; others say the US will go into recession in 2028; some say China has the means to win WWIII while others say there's no chance anyone could beat the USA. You're unfortunately still in a phase where you can only rely on external interpretation.
1. There is no mechanism that can force a sub to surface. Do any of your sources claim to know how you can do this? Or do they give you an empty conclusion?
2. Having a submarine's true stealthy acoustic signature figured out is detrimental to the sub, but if it knows you're recording, chances are, you're not recording the true acoustic signature. This is not just for Chinese subs.
3. Nobody claimed that the flag was there for sovereignty. I said it's a "Mission accomplished, see you next time" taunt.
These have all been pointed out to you. You can quote as many people you want but (false) credentials don't trump logic and quoting 1,000 "experts" saying the same thing doesn't mean it will be true if it doesn't fit logic. In other words, 1,000 people can say that a sub was forced to surface, but if there's not a way to do that, they'd still all be wrong. If you wanted to counter this statement, the only way you could do it is to provide a way for which it could be done. Even then, you would only prove the possibility, not that it actually happened.
Lastly, again, whether the flag-raising was a threat or taunt or something else is speculation, but I've never heard of any country in the world that raises their national flag to surrender. Maybe your country does; I don't know, but usually, it is the white flag for surrender. The national flag means pride.
Your fantasy story is reminiscent of "The True Story of Ah Q " by Lu Xun.