On the scale of events... non-sync battery FW is a minor and "should be" easily resolved and "should have" been prevented by performing an update to each battery as required. From what I've heard / read, these incidents are more Pilot error for not performing the updates as technically outlined in the FW upgrades.
Overall, if one negative report incident detours attention to that brand, there isn't a brand to purchase. Yuneec has experienced problems, recently on the enterprise side the H520 has experienced IMU failures and falling dead.
Hopefully for all devices, brands and the Engineers designing, these incidents evolve into improvements... the outcome should be positive and beneficial to all or the company likely fails.
I'm not quite understanding the severity of this particular "noticed" failure when previous FW & apps have addressed a method to prevent non-sync'ed batteries. Plus this is a pricey Enterprise craft, not a prosumer craft, indicating it should be primarily owned by competent Owners. But at the same time, I commend any company: Yuneec, DJI, Chevy, Ford, etc to step up and make the announcement and correct.
The M600 incident is new to me... a few quick searches pulls up zip on any issues you've described. With the number sold without the inside contacts you're privy, I'd assume I'd hear of large Matrice 600 platforms crashing.
I too own both M210 & M600Pro... great crafts! I maintain FW, Sync FW, monitor battery conditions and routinely inspect beyond the checklist. Unless there is a unforeseen electronics failure, I'm confident I'll catch the normal mechanical failures in the AC.
I'm also in the planning for a H520 in future despite the various posts of it's dramatic drop failures. Very sorry for the Owners, glad several have received replacements and I'm confident the problems will be resolved.
Glad to see this Notice being broadcasted, obviously the correct procedures have been ignored and it's become a concern for DJI; Or avoidance to upgrade older FW despite upgrade highlights touching on the upgrades.