I believe half of this effect stems from using enormous quantities of high-grade activated carbon in Amano's filters. I'm a regular user of activated carbon, and, together with water professionals, I often observe improved clarity of water treated with AC.
Questions remain, though, on quantity of AC, its quality (from coconut vs. from coal, acid washed, a.o.), and periods of replacement. I suspect that Amano - with his budget - knew well why he opted for high quantity of the best of all activated carbons available.
Myself, I study AC effects in long-term horizon, yet I don't dispose of Amano's budget, that's the difference, I'm afraid. BUT I strongly suspect that cheap Asian AC's made from coconut (they form majority on the market) perform poorly for our purposes, thus I'm using solely AC made of coal, plus I wash it in acid before use (rather bothersome job).
Now, WHY does AC make the water clearer? Two effects. Firstly, it traps dissolved organics, of which some colorize the water. Secondly, by trapping dissolved organics, it makes the water "hungry" - unable to feed free-floating microbes.