Hello Robert,
If the temperature is low enough to freeze a conventional hose, it will also freeze a flat type hose. How a flat hose will cope with being frozen I don't know, but I suspect if it freezes with high pressure water inside it might be more likely to split compared to if teh water pressure is low and the pipe has not fully expanded.
Your thread title refers to "fresh water" and you need to be aware that unless a hose is sold as food grade, it may have been manufactured using some quite unpleasant materials that might leech into the water passing through the pipe, and thus into your caravan or motorhome. Boiling the water may well kill any bugs but it won't affect the toxicity of any chemicals.