When I read about Giant, they talked about how in the past road bikes have to be in like 10 incremental sizes, but Giant had an idea from a mountain bike (which usually only have S M L sizes) to make road bikes with compact geometry so that it can be made with bigger jump in sizes.
How does this work? why a traditional frame can not be made in the same jump in sizes?
No matter how I compare the frames, I can't wrap my head around how a compact geometry can cover wider possibility of sizes that the traditional frame does not. The head tube angle is the same, the seat tube angle is the same, so raising or lowering stem and or seat post will be no different regardless if it is a traditional or compact. It is not like compact geometry can have adjustable stack and reach.