Anthropic seems to have chosen their in-house philosopher well - one who’ll be amenable to getting confused in their favour.
I don't think many people would say an LLM written in Python is conscious BUT an LLM written in Excel is not.
People just don't ascribe consciousness to things that can't converse (or at least emote or give the appearance of emoting), and spreadsheets don't do that.
The reason people are debating the consciousness of LLMs is - obviously - that the LLMs generate sufficiently plausible text that people using them think they're having a two-part conversation. Like I think I might be having a two-part conversation now. Turning your question around, why do you think Hacker News posters are conscious? You have no direct evidence they are.
Clearly consciousness is an emergent property of certain kinds of network, independent of the substrate within which the network exists.
Difference in size and complexity and nature of calculations being run?
I'd ask the other way - why do you (general you, people who do not have this inkling) have no problem debating consciousness of meat based brains, but it somehow becomes a category error when talking about silicon? Assuming you don't believe in divine magic, and that divine magic is core to consciousness, there's no reason to assume it's impossible a complex enough machine running complex enough software could be intelligent, or conscious - thinking is computation, and computation is made of math - it's independent of substrate that does the computing in the real world.
LLMs are definitely a different beast than regular software - both in their structure and in their generality. They may not be conscious or intelligent, maybe this specific design could never truly be (though I think it could) - but bucketing them with spreadsheets and terminal emulators is a real category error. If you stop fixating on the underlying substrate, then LLMs are already much more similar to biological minds than to any "regular" computer programs.
But that's still somewhat abstract. In immediate practical terms, it's also why I keep saying that anthropomorphising them gives a better high-order intuition: they are, by design, emulating human thinking in full generality, which makes their overall behavior, including their well-known problems like hallucinations or prompt injections (i.e. manipulation/gullibility), match what you'd expect of a people-like component of a system. It's a real, dangerous mistake, to treat LLMs like regular software components when designing systems.
When doctors are testing if humans are conscious they'll do things like hold out their hand and say how many fingers am I holding up. Some LLMs can pass that.
I personally believe all information processing machines possess some level of consciousness.