The Star Forge is a factory, so there is technically nothing wrong with producing multiple items of the same design. Moreover, it would be strange if a factory could not produce several products of a known design from the same parts.
What may seem wrong is the name of Darth Revan's Robe. The one unique Star Forge robe that Revan once wore and may have modified for himself, was destroyed by Jedi Council. The new ones are just similar mass-produced darkside Star Forge Robes.
But since the description of lightside Star Forge Robe mentions that “these robes were customised using an analysis of the Jedi they were created for”, I suppose that means, all robes created for Revan, would not be the same if they were created for other people. Hence, “the Darth Revan's Robe” will simply mean clothing designed with the physiology of Darth Revan in mind.