All batteries have a temperature range that specifies their...

All batteries have a temperature range that specifies their optimal operating conditions. Outside this range, you’ll have problems, no matter what the chemistry of the battery.

This is something that should be considered when installing a battery system. If the battery is being installed somewhere that typically has sub-zero temperatures, the system should be designed to handle that - whether by insulation, heating systems, or some other means.

I can state from experience that the Redflow battery does generate some heat; whether that would be sufficient in a given location is a question for the installer to answer.

If the system isn’t designed to handle the conditions at its location, the installer is incompetent. That’s not a function of the battery; the battery only exposes that incompetence.