Since the release I've had the chance to chat with a handful of analysts working specifically on verification of blockchain/cryptocurrency/DLT systems, and can confirm that they also use the usual distsys sense of "safety property"--namely: "something bad does not happen".
I'm not sure how widespread this understanding is in the DLT space (still looking for a citation for RDX Works's definition) but the researchers I've talked to were unanimous: losing committed transactions *is* a safety error, even if every validator agrees to throw away data.