Unless you have any evidence suggesting that one or more of the variations of the Church-Turing thesis is false, this is closer to a statement of faith than science.

Basically, unless you can show humans calculating a non-Turing computable function, the notion that intelligence requires a biological system is an absolutely extraordinary claim.

If you were to argue about conscience or subjective experience or something equally woolly, you might have a stronger point, and this does not at all suggest that current-architecture LLMs will necessarily achieve it.

There's a big difference between "this project is like time travel or cold fusion; it's doubtful whether the laws of physics even permit it" and "this project is like heavier-than-air flight; we know birds do it somehow, but there's no way our crude metal machines will ever match them". I'm confident which of those problems will get solved given, say, a hundred years or so, once people roll up their sleeves and get working on it.

"Biological activity" is just computation with different energy requirements. If science rules the universe we're complex automata, and biologic machines or non-biological machines are just different combinations of atoms that are computing around.