That is not at all the thing you said. You said two objects moving away from each other each at the speed of light in non-expanding space would be perceived by each other as going at double the speed of light which does indeed not work like that in relativity.
That is not at all the thing you said. You said two objects moving away from each other each at the speed of light in non-expanding space would be perceived by each other as going at double the speed of light which does indeed not work like that in relativity.