Both methods give good results, so neither is really better. One advantage to not brazing the ends in is that you have leverage from the tip end also, to force the bend in where you want it. If you are tip trimming anyway.

I think the factories bent forks, not blades, I`m sure some start with pre-bents also. But I have seen big machines that were designed to bend both sides. It makes sense to have such machines in shops that tune up forks also, since they are forced to deal with the fork in finished form. Beats sticking them under a door. Obviously a machine on that scale is more expensive to build.