Exactly. The Han Unificiation project never tried to unify everything. They just took the set of common characters and unified them, leaving the rest alone. They may have made some mistakes in choosing which characters to unify, but for the most part they did a splendid job.

Korean (Hangul) has its own, massive block of over 11K code points. Japanese (Hiragana, Katakana, and other assorted symbols) also has its own block outside of the Unified Han block. Chinese characters that are clearly distinct get their own code points as well. How else would I write 国 and 國 in the same sentence?