If we (like I do) assume a materialistic world rather than a dualistic one, then we can make the assumption that a complex structure is needed for reasoning and sensing. Even if we postulates that this is true, then if you limit your definition of consciousness to the combination of a subjective experience and that, then indeed we are talking about different things.

(Ironically, the authors argument pushes things towards a dualistic interpretation, because in a purely materialistic universe there appears to be no other possibility than computation to produce a complex consciousness, irrespective of what adds a subjective experience to it - e.g. any unknown physics allowing consciousness would in a materialistic world just be another form of computation -, but a dualistic interpretation would undercut his entire argument - with a dualistic conception of the world, none of the arguments he use would prevent a possibility of some out-of-universe "spark of consciousness" imbuing anything and everything irrespective of in-universe logic)

But we have no evidence to suggest whether the subjective experience - I used that term for a reason - part of that, which is the very core of what would distinguish consciousness from "dumb" computation requires complex structure or not.

Part of the problem is that a whole lot of complex structure is required before we can interrogate something about whether or not it is conscious, and even then we struggle to find ways of telling whether it is "just" mimicking consciousness, because we have no measurement to apply to tell us whether something is conscious or not, just whether it appears to be.

I have aphantasia. I don't see things in my minds eye. I went decades before I realised this is unusual. People who hear about it get confused about how I can e.g. remember what something looks like, but I can sketch out in detail what things looks like (I used to draw - not great, but better than average), and I can "visualise" complex relationships that I can't visualise - I know how they link together even though I can't see it. To me, that experience makes me perhaps more willing than average to accept that reasoning and the subjective experience of reasoning might be surprisingly separate, and to at least be open to the possibility that the reverse could be true as well - that entities that lack the complexity required to reason might still have a flicker of subjective experience.

To be clear, I don't believe that is the case - I simply don't know. But I also don't deny the possibility, because we don't know. We have no data to point in either direction, and so when someones argument requires ruling it out in order to support their argument, that argument is on shaky ground.