Manufacturers don't reveal production data as they don't want competition to understand their market share, sales trends, market segmentation, or the like. The manufacturer's don't reveal anything that may be used in some other entity seeing competitive opportunity or in deducing the manufacturer's strategy. That is common. It is unusual than any manufacturer in any industry releases any production or sales/volume data.
A manufacturer may later release data once the product is no longer sold to serve some other purpose, or out of some other interest such as releasing muscle car data to hobbyists in attempting to reinforce brand loyalty or their manufacturing 'prowess' (corporate testosterone!).
Or, a company may expose data to comply with Legal orders (such as is the case with NHTSA recalls).