It's not a bug, it's a legitimate warning.
On Broadcom 12gig SAS HBAs "firmware version=driver -1"
Josh Paetzel contacted Broadcom about this some time ago and code was put in place to account for it.
FreeNAS 9.10.2-U3 updated the MPR driver to Phase 14 aka 15.01.00.00-fbsd.
To match, the firmware has to be bumped to 14.00.00.00.
For 9300-8i users, they would need to use this following package:
9300_8i_Package_P14_IR_IT_FW_BIOS_for_MSDOS_Windows.zip