I have no idea what current numbers are, but I expect long term most factories will be inland and produce wind turbines of a size that is limited by local transport roads/laws. At sea might be better, but one factory can produce windmills for any ocean in the world. Inland shipping is far more expensive and so we need more factories scattered around.
If your country is near the sea then off-shore wind is best. However a lot of land isn't close enough to the sea to make off-shore practical and so they need a different option.
Large scale composites are still largely manual labour, and there are few pieces of tooling which themselves need to be one big piece. Mould can be split into sections rather easily.
Most wind farms (on shore) are in fields that the farmer has planted. you want to disturb the crop as little as possible while installing which means the factory will be elsewhere so that you don't need to tear up more crop in manufacturing.
https://www.theverge.com/22296979/us-offshore-ships-wind-boo...
New Details on First Jones Act-Compliant Wind Turbine Installation Vessel:
https://gcaptain.com/new-details-on-first-jones-act-complian...
U.S. Customs and Border Protection Expressly Applies Jones Act to Offshore Wind Projects in U.S. Waters:
https://gcaptain.com/u-s-customs-and-border-protection-expre...