PRNG is a mechanism to produce randomness from an initial random seed, so basically a way to derive more secrets from one secret.
Looking at the Wikipedia entry for KDF you find
In cryptography, a key derivation function (KDF) is a cryptographic algorithm that derives one or more secret keys from a secret value such as a main key, a password, or a passphrase.
Which sounds to me like what PRNGS are. So will it be correct to classify PRNGs as KDFs?