You're assuming that the water cools instantly and you're always wasting the run from the boiler to the fixtures. This isn't the case: the big advantage of the zoned approach is that the trunk will remain warm if you're using multiple fixtures branched off the same trunk.
So if you have a shower while your washer is in use, you only waste that little branch of water, rather than the whole trunk (or the home run in the manifold approach). Or if you wash your hands and have a shower in the same bathroom within half an hour (for example). With the manifold approach, you lose the efficiency savings when you use the sink / washer / shower within half an hour of each other.
You're assuming that the water cools instantly and you're always wasting the run from the boiler to the fixtures.
No, I'm just assuming that the definition of a "cold start" is that the water is allowed to cool before the next measurement is taken. The alternative (which I agree is common) is a "hot start". The author defines these terms on the box on the bottom left of Page 76 (which I don't seem to be able to copy and paste). Since the chart explicitly says "cold starts", my question/complaint is that as labelled, I can't see how the chart can be correct. I agree that measuring a blend of hot and cold starts is probably a better metric to judge the systems by.
So if you have a shower while your washer is in use, you only waste that little branch of water, rather than the whole trunk (or the home run in the manifold approach). Or if you wash your hands and have a shower in the same bathroom within half an hour (for example). With the manifold approach, you lose the efficiency savings when you use the sink / washer / shower within half an hour of each other.