[mbed-tls] Exports from the shared libraries vs API

Hi, I am trying to identify the API available by looking up exported symbols from the built shared libraries libmbedcrypto.so ,libmbedtls.so and libmbedx509.so. I noticed that many of the exported functions are not documented here https://mbed-tls.readthedocs.io/projects/api/en/development/ . My question really is, are those functions exported through the shared libraries intended to be so ? For example, function mbedtls_mpi_core_add does not seem to be part of the API but it is exported. Is this intentional ? It's not uncommon that functions would be exported but not part of the API, I just wanted to get some clarification if possible regarding the reasons for doing so in the case of MbedTLS. Thanks Ahmed