Snow can be placed on blue ice

Works as intended. Blue ice is a solid block, so snow layers can be placed atop it, while packed ice isn’t.

The definition of "solid" is very inconsistent. You suffocate in ice, packed ice, and blue ice, making them all "solid" blocks. You can't walk through them, making them "solid" blocks. You can place torches on the sides of packed ice and blue ice, making them "solid" blocks. Packed ice not having snow layers form on top is most likely because of how it naturally generates with exposure to the sky, and the devs likely don't want snow layers forming on the ice spikes in the respective biome. This makes packed ice an exception. Blue ice, however, does not naturally generate with exposure to the sky, so there's no issue if snow layers form on top or not. An argument could be made for consistency, but in the end it would be WAI, just for a different reason from what you described.

In some cases blue ice can be exposed to the sky, that's how I discovered this "Bug" Whether or not this is a bug is debatable.