You don't understand why I would challenge you to cite your sources in a thread discussing COVID-19 conspiracy theories and misinformation? Not to mention, I think it's pretty clear to both of us that this "well documented event" is not common knowledge to people who don't follow COVID conspiracy theories.
I think this event qualifies as “well documented” by any reasonable standard, there was official public disclosure and an open investigation.
As one quick example, here’s a news clip including an interview with the Taiwanese health minister discussing details of the (then) ongoing investigation:
The author is saying that there was a lab leak involving delta, not that delta originated via a lab leak.
The latter claim would indeed be a red flag, but the former is just describing a very well-documented event.