I haven't yet managed to fit inside a toothpaste tube. But you believe in the impossibility of this right? There is no absolute belief or disbelief. It is all a continuous gradation. Some things we can bring ourselves to belief in if there is sufficient cause. Not arguing for or against the original point but just your argument and condescension.

I believe I cannot not fit into a toothpaste tube for entirely different reasons than "nobody has ever done it." The latter is the assertion here.

Stating that it has yet to be done is a fact --- and facts are not ignorance

Stating that it has not been done has no implications on whether it can be done, which is the claim being made.

Stating that it is "just chemistry" has no implications on whether it can be done, which was the claim being made.

The fact that it has not been done with "just chemistry" is no proof but it does tend to skew the probabilities toward the view that substantially more may be required.