Some people use the word "conscious" almost interchangeably with terms like "intelligent", "creative", or "responds to stimuli". Then people start saying things like LLMs are conscious because they pass the turing test.
However, others (including the authors of this paper and myself) use the term "consciousness" to refer to something much more specific: the inner experience of perceiving the world.
Here's a game you can play: describe the color red.
You can give examples of things that are red (that other people will agree with). You can say that red is what happens when light of a certain wavelength enters your eyeball. You can even try saying things like "red is a warm color", grouping it with other colors and associating it with the sensation of temperature.
But it is not possible to convey to another person how the color red appears to you. Red is completely internal experience.
I can hook a light sensor up to an arduino and it can tell me that an apple is red and that grass is not red. But almost no one would conclude that the arduino is internally "experiencing" the color red like they themselves do.
While the paper is using this more precise definition of consciousness, it seems to be trying to set up a framework for "detecting" consciousness by comparing external observations of the thing in question to external observations of adult human beings, who are widely considered by other adult human beings to be conscious entities [1]. I don't see how this approach could ever produce meaningful results because consciousness is entirely an internal experience.
[1] There is a philosophical idea that a person can only ever be sure of their own consciousness; everyone else could be mindless machines and you have no way of knowing (https://en.wikipedia.org/wiki/Solipsism). Also related is the dead internet theory (https://en.wikipedia.org/wiki/Dead_Internet_theory).