Thanks for your patience here, the reason we were having issues finding information on that second message is that it’s a linux message, rather than HiveOS specific.
The /etc/moduli file contains prime numbers and generators for use by sshd in the Diffie-Hellman Group Exchange key exchange method. Modulus itself is in hexadecimal. When performing Diffie-Hellman Group Exchange, sshd first estimates the size of the modulus required to produce enough Diffie-Hellman output to sufficiently key the selected symmetric cipher. Sshd then randomly selects a modulus from /etc/moduli that best meets the size requirement. The Diffi-Hellman key exchange is used in the beginning of SSH sessions to generate a shared secret between the client and the server. During this, the preferred file size for the key exchange did not match and therefore, for this one session, the default modulus was used.
For more information, please visit: https://entropux.net/article/openssh-moduli/