This is the part I have to disagree with. If AGI turns out to be emergent and depends on scaling up simple mechanisms, that emergence is all the "explain consciousness" you need. Dogs, corvids, octopods, bononos, etc. do not have human intelligence but they all have brains that perform some tasks our brains perform. That suggests that a combination of scale, a particular set of architectural parameters within the range of possibilities of mammals, and, maybe, some unique variation is what it takes to make a human intelligence. Nobody explained consciousness before we labelled this thing "consciousness."