Yes, they did have auto-repeat for planetary projects at one point, but that was the only way the worked. This meant that, as new terraforming became available, one would need to cycle through all planets to stop the projects. Additionally, this also auto-repeated garrisoning legions, which meant that if not careful (and very micro-managey) all available legions would be garrisoned on a single planet, with no way to remove them from this unwanted result.
In fact, having an option to auto repeat or not is the best solution. But it may be problematic to code that in, depending on how it was programmed.