How the Kongo class became fast battleships

Were the rebuilt Kongo-class ships still battlecruisers?

No; their extensive reconstruction and altered proportions made them fast battleships, though not ideal ones.

Their reconstructions added roughly 4,772 tons while changing protection, machinery, and hull proportions. That growth was far more than a cosmetic refit: it shifted the ships toward the protection-and-battle side of the spectrum. The Japanese description of them as fast battleships fits the rebuilt ships, though they were imperfect examples. Their battlecruiser origin remains historically important, but it does not override what the rebuilt ships had become.