I think here is another mechanic shown. In your environment is the old inventory plugin active for the iLO firmware. This old inventory plugins are not supported anymore from 2.2 on.
As i wrote the firmware inventory i also saw this message. Until now i had no time to update/upgrade the inventory plugin for SNMP.
All these messages have nothing to do with core functionality inside CMK. It is only an advice to look at the installed plugins.