Yup, apparently so - but "The Mind's Eye" must have already been shot with the idea that the character was Yar re-reincarnated. What else could it have been all about? Foreshadowing of that sort makes little sense for an all-new villain character.
Cosby wasn't used for the actual shoot as there was no practical need to hire and schedule this expensive and busy actor when a cheap extra would do. But the cheap extra had the physical attributes of a Crosby/Yar character, and probably not by chance. So yes, retroactive looping, but most likely not retroactive storytelling.