I've changed brake hoses a bunch of cars with that tool and it has never let me down. You can apply it as tight as you physically can and it will not damage the nut. It will not slip.

I usually cut the hose off so I can use a deep socket on the fitting with an 18-inch breaker bar for extra torque. I changed the original hoses on a friend's '71 250c a few years ago. They broke free with a crack that made me fear at first that I had snapped something. Every one came off without a hitch.