I agree that "not blocking on Weibo" is kind of official. I made similar point in another post by saying "there is no need for pushback because Li has said nothing different from the official line".The mainland audience may not have been on embassy minister Li's mind when he issued the threat, but the way the mainland media reported on it so freely is extremely telling. I must emphasize again the lack of official pushback, since it's well-established reality that the government exerts efficient and comprehensive control on what stories can be reported on and shown in domestic media. You said before that Weibo is not official media, but this distinction is less important than you might think. Many leaked government statements regarding content that can and cannot be shown on Weibo essentially amounted to official edicts on censorship. Cooperation with official censorship policy on Weibo has become quicker and more efficient in the past year due to recent public discontent from officials about past excessive dissemination of disapproved content through microblogging services. The government has clearly made some sort of decision as to whether Li's message was too extreme or inaccurate to be widely disseminated domestically.
But I think "doing nothing to block or stop" is not the same as "purposefully actively propagating". Remember, Chinese government can and will block it if it feels the sentiment goes too far (even it is right) just like their "not blocking". Censorship works both ways on either directions regardless the right/wrong of the subject. It is only meant to keep things in check. There for it is telling something, but nothing extreme or fundamental.