ipmi_authtype in hosts table is set to -1 (IPMI_AUTHTYPE_DEFAULT) when creating new host via frontend.
Server uses ipmi_authtype to decide whether IPMI configuration including (empty) username and password should be kept for the particular host in the configuration cache. Specifically if ipmi_authtype != 0 (IPMI_AUTHTYPE_NONE) then configuration is synchronized.
In dbschema.c the default value for ipmi_authtype is also 0 however this might be to accommodate templates that are also stored in the hosts table.
In summary: server and frontend do not agree on the default value of impi_authtype (-1 if frontend, 0 in server).