I had read it carefully. While you are focusing on one particular part of the post, I am focusing on a different part of the same post, specifically It is not clear there is any value to doing this as you would never want to use an IR virtual device with FreeNAS. and further explains We used to do this in the old days for boot devices, but with ZFS boot this may no longer relevant.. Prior to being able to boot from ZFS, you had a different filesystem for the boot device and would want that device on an HBA with IR firmware to provide mirroring.
I am not sure what is scary about the advice to flash an IR HBA to IT, as had been the recommended best practice for over a decade (when did that change, when did it become acceptable to use IR firmware with TrueNAS, with the SAS3 HBAs?). It adds one, fairly simple, step to the process of building a server. I also note that most of the HBAs on the used or new old stock market being sold for FreeNAS / TrueNAS use are already IT firmware (for as little as $25).
We should be recommending the best solutions, but I agree that we should also be acknowledging solutions that would work, but would not be the best. I did not do a very good of that above, and for that I apologize.