This is a theory put forth by:
The facts observed:
1. Shi Zhengli et al from Wuhan Institute of Virology published a paper at Nature in late January 2020 that said nCoV is the most similar to bat coronavirus to nCoV is bat RaTG13 (~96% similar at RNA level). The RNA of this virus was discovered in bat fecal samples collected in 2013.
https://www.nature.c...1586-020-2012-7
https://www.ncbi.nlm...core/MN996532.1
2. RBD area of the Spike protein of RaTG13 is highly similar to SARS.
3. The Envelope protein of nCoV is 100% identical to RaTG13 and also two other bat coronaviruses ZC45 and ZXC1 found in 2013.
https://www.ncbi.nlm...uccore/MG772933
https://www.ncbi.nlm...uccore/MG772934
4. Ratio of nonsynonymous to synonymous change is 5:1 between ZC45 and ZXC1 but it is 44:1 for RaTG13 and nCoV. The similarity between ZC45 and ZXC1 is ~97%.
The arguments suggested by the author:
1. RaTG13 was fabricated and never existed. Since Shi Zhengli et al didn't have the bat cells infected with RaTG13, it is not possible for other scientists to reproduce the RaTG13's sequence. RaTG13's Spike protein is very similar to SARS indicating high possibility of infecting humans. Therefore, Shi should have published the sequence in 2013 instead of 2020. The most likely explanation is that Shi Zhengli et al simply used nCoV sequence and then modify a few ACGTs and submit it to public database and name it as RaTG13. This explains why the ratio of nonsynonymous to synonymous change is so much higher than more natural value of 5:1.
2. It is highly unlikely that the Envelope protein doesn't evolve at all from 2013 to 2020 as it has nothing to do with infectiousness. In fact, newer nCoV has slightly evolved Envelope protein relative to the original nCoV,
3. If RaTG13 was fabricated, most likely nCoV was designed using ZC45 or ZXC1 as a template such that the Envelope proteins are identical.
I would say the arguments make some sense. I personally now think it is more than 50/50 that nCoV is made at Wuhan Institute of Virology.