What crashtestmonkey said, and even within ‘open mould’ designs there’s infinate different permutations of layups and materials, so two visual identical frames won’t feel the same.
I think you’re implying in your last post that the frame’s aren’t customised to the rider, which whilst true, probably isn’t an issue as there’s 100’s of manufacturers producing 1000’s of designs in 10,000’s of size combinations, somewhere out there is a bike that fits what a customer wants.
Probably more ‘custom’ than building ‘custom’ steel bikes, there’ll be a few uniquie finishing touches, but they’ll all use combinations of the same few tubesets from Reynolds, Columbus, Deda, etc, whereas the designer/engineer at Giant might have entirely different ideas on how to make the tubes themselves than his counterpart at Cervelo.