- Virus infects human ACE2 suboptimally, therefore it's not lab grown. Why? Because a virus engineer is always going for maximizing spread rate? Seems plausible that less-than-ideal infection rates of humans could be a feature rather than a bug.
- A polybasic clevage site was not seen in SARS-CoV... but it's function is not known. Okay?
- The virus backbone was "0day" and not previously known to researchers. Seems like a feature that a covert bio warfare lab would desire.
The rest of the speculation seems to ride on the assumption that the virus originated in China (despite evidence showing otherwise[1][2]), and their discovery seems biased toward any data to support that conclusion.
1. https://academic.oup.com/cid/advance-article/doi/10.1093/cid...
2. https://link.springer.com/article/10.1007/s10654-020-00716-2
You are correct. There is both gain of function and loss of function happening in these types of experiments.