Since
@cduggles tapped out in frustration, I'll try and take this one.
Let's start with the word "natural", which is used precisely 10 times in the article, 9 of which as a part of the (unless there have been some significant developments since I last did a biology class) very much empirically supported term "natural-selection". The other instance of its use is in the term "natural evolutionary process" - hardly as particularly contentious claim to make given all the references to natural selection.
The term "very likely" occurs exactly zero times in the article. The term "probable" occurs a similar number of times, zero (unless of course you want to deconstruct the word improbable, but really that's pushing it).
On the pre-assumptions part. I hate to be the one to break this to you, but all science is based on assumptions. Identifying and stating those assumptions is an essential part of the research process. For example, let's say I wanted to research the theory that 1 + 1 = 2. What I'm going to do is get a set of 100 1's and another set of 100 1's, randomise them and run the following equation on it for (i=0;i<100;i++) Set A(i) + Set B(i) = datapoint. On the face of that, it looks sound. I add 1 + 1 100 times and check how many times that the answer is 2. There are assumptions here. In this case, I am assuming that all of set A and all of set B are the value 1. What if they aren't? What if there is a 2 in there? These things happen. These things happen ALL the time.
To deal with this issue we use two main methods - first, we clearly state our methodology, including our assumptions, so that someone else can repeat the work and check their results against ours. Secondly, we don't ever (as in big science no-no, as in stop reading if you see a purportedly qualified scientist do it) state things with certainty. We state things in terms of probability, statistical probability in our results. In our discussion we use terms like "The evidence suggests..." "The evidence strongly points to..." "The overwhelming result...". We don't ever say "We have proven...". You see, it's the media (largely influenced by procedural courtroom drama) that goes out asking for and frequently misquoting scientists as saying they have proof, or that things are proven.
Scientists, like
@cduggles so valiantly tried to explain to you are skeptical. Even when everyone else is out there triumphing over the solving of the great mystery, scientists hedge, because they aren't police detectives. They aren't in the business of closing cases. They are in the business of leaving them open so that they can be questioned, challenged, expanded upon and debunked as new information dictates they should be.
The paper you've posted there doesn't appear particularly outrageous or shameless to me. It seems to be appropriately written, and given its context as an early investigation into the origins of this particular coronavirus is well considered and reaches reasonable conclusions, while clearly stating in its limitations section that further research is required. The counterpoint to this article that you've posted is a youtube video with the word ass in the title, and in my previous research on such videos the evidence supporting the assertions made in such videos has been weak (n=toomany, CI = 99%).