This is a semi-interesting piece (because of how poorly written it is and how hilariously confident the writer is), but it is embarrassing that the person writing claims to have a PhD in at least something semi-related to molecular biology, yet is trying to convince people that we can use independent probability when dealing with protein amino acid sequences. Certain sequences are seen time and time again in nature, just like certain traits visible to the naked eye have evolved independently. More importantly, this author dismisses natural mixing of SARS and HIV1 as "ridiculous" and provides no other explanation. It is possible that SARS-CoV-2 was created in a lab, but it is also possible that HIV-1 and SARS-CoV-2 co-infected a host.

Edit: to elaborate, certain amino acid sequences are seen again and again, and others are practically impossible to see in nature because amino-acids fold into 3D proteins...and each amino acid is like a Lego piece. There is a lot more detail needed to understand fully how tertiary and 4try protein structures form...but it is also possible to understand it decently well after an undergraduate degree in biology, chemistry, biochemistry, etc. A PhD in the field knows this inside and out. If I had to guess, the author of this post has a PhD in something like statistics or computer science, and thinks that they can apply high school level math to two fields (molecular biology and biochemistry) that they do not even have a high school level of understanding of.

To make a very stretched analogy (I am a doctoral student in the life sciences and a hobby programmer), this blog post is like saying that some Java source code is stolen because four of the class names are the same between two projects, and then using the number of possible characters in the class names and the length of the name to run some statistics. The problem being that no one has class names like "AeNOQ92bA"...in fact the vast majority of 8 character sequences will never be class names. Just like the vast majority of amino acid sequences (likely) do not exist in nature. And then you dig deeper and find out the class name is something like "MainDashboardSupervisorTree" (I do not know Java so forgive me). Then you also find out that the author of both classes...is the same guy who moved companies and likes particular naming convection, but never meant to copy stuff word for word. Similar to how SARS-CoV-2 could have naturally incorporated HIV-1 RNA into its genome when co-infecting a host.