Yes, this was an unnecessary step. Draining the trans AND converter, changing the filter and filling with fresh fluid is the best approach.

Something very important to point out here is the SMELL of the fluid is probably a better indicator than the color. If the fluid is nice and red, there's no need to smell. If it is brown or black, smell it. If it smells like turpentine or varnish, then your clutches are burned. Under these conditions an aggressive flush can often wash out the clutch linings and the car won't move.

If the fluid is brown, but smells okay, just change filter and change ALL the fluid.

Good luck,