So the optical design has nothing to do with the bellows length, both lens sizes being equal
Yes, so they need equal extension for the same reproduction ratio.
But for stuff closer up, (say an occasional jewely shot) won't the macro be a better option
Yes
...is the normal version much better lens at everything else above 1:3 reproduction.
1:3 is a reduction - subject three times the size of the sensor... with a 50mm sensor the macro would be better for subjects smaller than A6 (about 105mm * 145).
What I call close-up lenses (usually described by the manufacturers as Macro or even micro) are OK for 1:1 to infinity,,, but what I call proper macro lenses are normally optimized for 1:3 to 3:1... but I have a set of Luminars, each optimized for a different range of ratios, and they together give me 1:1 to 40:1.