Pretty obvious. As it is now building ships in large quantities is done by spreading the job across large amount of provinces, which is neither fun nor realistic and eats up computational resources. Reduction in building time through shipyard building somehow alleviates the problem, but if it was to truly match parallel shipbuilding the build time reduction would need to be absurdly high.
I propose that instead, shipyard building will allow to build multiple ships in single province at the same time; scaling with diplo-dev. Something like lvl. 1 shipyard=1XDiplo-dev shipbuilding slots and lvl. 2 shipyard=2XDiplo-dev shipbuilding slots. Alternatively higher multiplier like 3X/6X with heavy and light ships taking up multiple slots.
I propose that instead, shipyard building will allow to build multiple ships in single province at the same time; scaling with diplo-dev. Something like lvl. 1 shipyard=1XDiplo-dev shipbuilding slots and lvl. 2 shipyard=2XDiplo-dev shipbuilding slots. Alternatively higher multiplier like 3X/6X with heavy and light ships taking up multiple slots.