This is exactly why I mentioned the weather.

A scientific paper has to be verifiable, you should be able to recreate the experiment and come to the same conclusion. It's very very difficult to do with brains with trillions of parameters and that can't be controlled to the neuron level. Nothwithstanding the ethical issues.

We don't have a world weather simulator that is 100% accurate either given the complex interplay and inability to control the variables i.e. it's not verifiable. It'd be a bit silly to say we don't know why it's going to rain at my house tomorrow.

Until then it is a hypothesis, and we can't say we know even if the overwhelming evidence indicates that in fact that we do know.