I have zero experience with NiCopp tubing but I did notice on this site they advertise seamless NiCopp tube. If it's seamless it's probably not going to split and if it holds up with 45 degree inverted flares I would think it will be more than capable with AN fittings and how they have a ferrule backing the flare up.

https://store.fedhillusa.com/316475mmbrakeline-2.aspx