9/11 - Is the statement "2.25 seconds of free fall ... is proof" based on a fallacy?

Is the following statement fallacious or is it flawed in some other way or, in fact, not flawed?

2.25 seconds of free fall acceleration (agreed to by NIST) in the collapse of WTC-7, the third building to collapse at the World Trade Centre on 9/11, means that all resistance in the base of the building was removed which, in turn, means that all its 83 steel support columns failed at virtually the same time which, in turn, means that the columns must have been cut by charges which, in turn, means controlled demolition which, in turn, means both that the NIST report on the building's collapse is fraudulent and that the US administration had to be responsible for events of 9/11.
https://www.ae911truth.org/evidence/free-fall-acceleration

Just to add that I issued a $5,000 challenge in 2017 to provide 10 points that favour the "fire" hypothesis over the "controlled demolition" hypothesis for the collapse of WTC-7 and I've invited challengers to choose their own structural engineer to validate their 10 points while I have provided my own 10 points with favouring of hypotheses swapped. No one has responded to the challenge although I have engaged with passionate supporters of the "fire" hypothesis including Mick West of metabunk.org, nor has anyone, in fact, provided a single point favouring fire.
https://occamsrazorterrorevents.weebly.com/5000-challenge.html

First let's look at the statement

2.25 seconds of free fall ... is proof

Unless you are talking about mathematical or logical proofs*, you want to use the word "evidence." There is no fallacy here, it is just a claim. Fallacies would or would not appear in your argumentation to support the claim.

In terms of the justification, very few people are structural engineers and physicists, arguably the ones qualified to evaluate your argument. As a layperson, I would ask, "why should I trust your analysis over the consensus of structural engineers and physicists on the matter?" What is your background in this area? Have you published your findings in a peer-reviewed academic journal so that experts in the field can evaluate your work and respond?

BTW, my response is virtually the same for those who claim of have proof that climate change is a hoax, the earth is 6000 years old, the world is flat, etc. These things are all possible, but extraordinary claims that contradict well accepted knowledge require extraordinary evidence—evidence that has been vetted by experts in the related topics. If you can't convince the majority of experts that you are right, why should any layperson accept your views?

To sum up, you could be 100% correct with your argument logically and factually, but the factual part is far outside the area of expertise of most people (myself included) so the only reasonable position to take is provisionally accept the consensus of the experts.

* The word "proof" is also used in a legal setting, but that really means evidence as well.

Since the claims made in this argument require verification that I don't possess, I don't know whether there are factual errors in the argument or not. But given the structure of the argument, it can be fallacious in the following way:
The given argument is a chain of causality, where it is claimed that one event will have to cause/leads to the second event and so on until the last event is concluded (2.25 seconds of free fall acceleration means that....which means that...which means that...etc). One very common fallacy such arguments are prone to is the slippery slope<> fallacy. To verify whether or not this argument is a fallacious slippery slope, you need to ask yourself: How likely is it that one event in the chain is going to lead to the next? Are there other probable alternative events that can take place down the chain that may divert the route of causality to a different final event than the one proposed in the argument? If satisfactory justification is given for each event leading to the next all the way up to the final event, the argument won't be a fallacious slippery slope.