The comparison about surface areas is wrong. A creature could drastically increase its surface area by having many tendril-like appendages (i.e. hairy surface)

The comparison about surface areas is wrong. A creature could drastically increase its surface area by having many tendril-like appendages (i.e. hairy surface) and limiting the core body to consist of thin shapes. A fractal web of tendrils would dissipate energy far more effectively.