Congrats on your offer. I assume that you received an offer early because it involves a gap year and a college for mature students.
It doesn't matter what KCL thinks of you, unless you really hoped for KCL and Cambridge is second best for you. But Cambridge likes you, and even as second best it's not so terrible.
KCL appears to adopt a numerical approach to admission. Score x for yes, score y for no. Cambridge takes a more rounded approach and considers all relevant info, not just the LNAT score. Cambridge chooses to dedicate resources to this because, I assume, it wants its admission system to relate to its teaching system. Oxford ditto. KCL adopts a different model.