No. Brake lines run every which way. You only need them "up" where the bleeders are to form an air pocket that you can easily remove. So the caliper need sto be "up", where the line enters it is no problem. If, say, a caliper is mounted upside down so the bleeder is in the "down" position, you can still bleed the brakes but it will take you FOREVER and a lot of fluid. As a general rule the lines are mounted below the level of the master cylinder, other than that do what you like.