I can imagine how decoherence explains why we only experience descent along a single path through the multiverse-tree instead of experiencing superposition, but I don't think that's sufficient to claim that all consciousness requires decoherence.

An interesting implication of Scott's idea is that consciousness is timeless, despite our experience of time passing. For example, put a clock and a conscious being inside Schrödinger’s box and then either leave it in a superposition forever or open it at some point in the future. If we don't open the box, in theory nothing is conscious of watching the clock as time passes. If we open the box, there's a conscious being who can describe all the time inside the box watching the clock. When, to the outside observer, does that conscious experience happen? Either all the conscious experience happens the instant the box is measured, contrary to our notions of the experience of time passing and our understanding of how the physical state of the clock changes (e.g. the conscious experience of seeing the clock read 3:52 PM on Thursday should have happened at 3:52 PM on Thursday when the clock inside the box was in a superposition of physically displaying that time with very high probability), or else there would have been conscious experience the entire time even if the box was never opened, in order that the experience could happen at the corresponding time.

Which means we're all p-zombies until a specific point in the future when we decohere sufficiently to have consciousness up to that point.