Nope you don’t HAVE to export, but it can make life a bit easier depending on the complexity of what you are doing. Shaders will react to the colour directly from the plugin, EDIT: the shaders go on the child objects not the antiqua plugin as I previously said, s’cuse me END EDIT. If you can get away with this then you can get some nice animated effects - for example on a wave/water mesh I colourised the peaks using antiqua and applied a reactive shader to provide some froth only on the moving wave peaks. It was a little jerky due to the mesh resolution but otherwise worked well.
One other thing I often do with Antiqua is run a previously exported model through it again to build up more complex vertex shading than a single application can achieve. You have the 3 RGB channels to store info in so for example if you were preparing a mouintain scene and wanted to apply layers of reactive shaders to the peaks you could apply blue to the peaks on one pass. Export/reimport then apply red to a tighter in set of peaks, and repeat again to apply green to just the tightest points and edges. Very flexible.
I would rate Antiqua in my top ten plugins.
Cheers