This kind of argument is nonsense. It boils down to: "This previously solved problem is unsolvable."
The previous solution is a biological brain, and the future solutions are mechanical, but that doesn't matter. Even if it did, such arguments involve little more than waving one's hands about and claiming that there's some poorly specified fundamental difference.
It's a waste of time. These arguments always boil down to some "mysterious soul that only biological brains possess". It's theistic nonsense.
Even if current LLM architectures can't get to AGI, which I will believe, there's no coherent argument that can be made that there is no possible path to AGI with digital computers.
It could be as simple as simulating the top-to-bottom biology of a human brain! That's possible, just wildly impractical, so any arguments based on abstractions like logic, mathematics, physics, etc... go right out the window. They're obviously invalid. Only practical engineering arguments can possibly be valid.
"It's impossible for heavier-than-air objects to fly!"
The previous solution is a biological brain, and the future solutions are mechanical, but that doesn't matter. Even if it did, such arguments involve little more than waving one's hands about and claiming that there's some poorly specified fundamental difference.
There isn't.