No, not true.
All brakes lines are best done with a 45* double flare (assuming you use 45* fittings.)
The double flare is to reduce the likelyhood of a split or crack in the flare both first thing and over time.
Some confusion may be in that 37* flared fittings don't typically use a double flare but they do use a special sleeve and nut. However it is not so common to use 37* AN or JIC fittings for brake lines.
I've made plenty of stainless steel lines and double flared them.
For an easier to flare but still as good possibly better than stainless
try some Copper-Nickel brake line .
Grigg
