“Jet fuel can’t melt steel” is a claim that originated in the conspiracy theory world. The problem with claims that seem spurious is that if you ignore them you are accused of hiding from the evidence, and if you respond to them you are accused of being irrelevant or legitimizing bad facts. I personally believe the “building collapse at freefall” is similar in being a slightly irrelevant argument— from my understanding, the collapse actually was slightly slower than that, I don’t believe a building couldn’t fall at a “freefall” speed given the massive amounts of energy involved, and any alternate explanation requires accepting several facts that I feel are far less credible.

That said, you are right that you can’t give any source unconditional trust and everyone must decide for themselves. But I’d add that we have to be careful with making unfalsifiable claims. If you say “I have no clue what happened … but I don’t believe [the official account]” there is no way anyone can refute your idea, because you haven’t given an argument about what did happen. Without a counter-hypothesis, you are just benefiting from the confusion and uncertainty around the debate.