The article which he quoted in length in 2019 [0] hasn't been modified and did mention both SARS and Coronavirus. He's just amending the quote he took from it.
Obviously the first time he quoted it, he didn't think it was relevant to show the example, so contracted it by hand to "[An example]" [1].
In 2020, he realises that specifically mentioning SARS and Coronavirus in a blog post about the dangers of biolabs causing a global pandemic will either seem relevant or look prescient so he adds it back into the quote [2].
This implies that in 2019, he had read the article and was aware of threats like coronavirus/SARS, but didn't think it was the important aspect of what he was discussing. So his crime here is a bit like rewriting your CV for a new job -- not lying about what you know or have done, but using different words that emphasize new aspects to the new audience.
[0] https://thebulletin.org/2019/02/human-error-in-high-bioconta...
[1] https://web.archive.org/web/20190331190550/https://dominiccu...
[2] https://dominiccummings.com/2019/03/04/the-most-secure-bio-l...