Wittgenstein kinda blows this burden of proof apart. Just because you can doubt something like the subjectivity of others to the point where it needs to be reconstructed from proofs, that’s an issue with the doubting experiment more than the subjectivity. Others possessing Subjectivity is the kind of hinge certainty upon which your world is constructed, it’s not a proof worthy endeavour to doubt it - it’s something you’re certain is the case. If it wasn’t then pretty well everything else about reality would be in doubt and needing constant reconstruction from proofs, which is an exercise in madness and futility, not philosophy. There’s really nothing in your experience where others not possessing subjective experiences of some kind really arises, except for the philosophical exercise of doubting and requiring epistemological proofs which can’t ever exist in the face of a relentless and unconvincable doubter. Heidegger talks about pretty well the same idea as Wittgenstein.
The argument you present like many arguments breaks down when the topic becomes self referential. It makes sense for other topics as analyzing subjectivity becomes pedantic when asking questions like why is the sky blue.
But now subjectivity itself is in question. The argument you present calls for the subjectivity of others to be taken as true because all reality breaks down if we don’t… but what’s suddenly stopping you from applying the same assumptions to an LLM? That is the heart of the problem. People are questioning whether the burden of subjectivity is applicable to LLMs.
Or another way to frame it… what makes humans rise to the level where we can assume their subjectivity is true? What is the mechanism and reasoning behind that? We can no longer simply assume human subjectivity is true because LLMs are now displaying outward behaviors that are indistinguishable from humans.
Also stop relying on the wonderings of old school philosophers. We are now in times where you can basically classify their ideas as historically foundational but functionally obsolete and outdated. Think deeper.