I think it's normal for the older size. All my 25.4mm bars are 25.4mm at the clam and either taper or step down to 22mm where the brakes go on. Same goes for the 25.4mm flat bars I've had.
I think it's a bit more complicated. There are plenty of Japanese drop bars around that are 25.4mm at the clamp, narrowing to 23.8mm (15/16"). There are also alloy all-rounder (flattish, swept) bars with the same dimensions. I own a GB pair. When 15/16" alloy bars were becoming more common, cheaper steel bars were normally still 7/8" at the ends.
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Que les branches hautes font,
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De ce silence profond.