I'll just answer myself. It is.
I had previosly updated TrueNas to Fangtooth which is not supported and I messed up the boot pool so I wanted to reinstall but was worried about it (I was thinking on just dropping HexOS and use TrueNas directly with the latest version).
I was able to reinstall everything following these steps (I had a recent copy of the truenas config):
Follow steps 1 to 6
Update TrueNas from the UI to Fangtooth
Reimport TrueNas config
profit
This was easier than I though and I didn't lose any data.
