I respectfully disagree with a counter-example, and regret only that Sheldon is no longer around to debate this, in his always-civil and rational fashion.

I geared my UO-8 45-42/13-15-17-20-23-26, with an ultra-6 freewheel, and I have a near-perfect ratiometric progression through all 12 chainring/sprocket combinations, including two eminently usable crosschains. The half-step in front helps, as does the close horizontal spacing and moderate cog size range in back.

With 1.5-step gearing and a standard 6-speed freewheel (14-26 and 13-23), I get 11 usable gears with the 2x6 combinations on the Bianchi and the Capo Modell Campagnolo. I avoid the somewhat rough-running large-large cross, but small-small works nicely.