That's a valid point for scanners, but its been deemed a bug in game.
I'm talking in real terms as i believe you were with your first quoted statement, terraforming would be something any race would aim to do if it existed and had the knowledge (we have the idea of it, but not the knowledge) Not just humans. As said, terraforming as we know it is a method of changing an atmosphere of a planet to suit a specific lifeform. Regardless of what lifeforms and what method it uses to do it, we as humans know that method to be terraforming. Whatever word it may be in an alien language, it would still be terraforming to us regardless of the composition of the atmosphere post terraforming.
Therefore terraforming is not related to humans solely
I never said terraforming was related to humans solely, I said the Scanner wouldn't know if an alien had terraformed a world. The way we know if a planet has been teraformed is through the scanner. The Scanner will be programmed to detect terra forming how humans do it. The chances of an alien civilisation using the same method is not likely even if the Alien race was human with same DNA but just from another distant planet.
When there are hyperdictions the scanner doesn't tell you the type of alien ship it is as the scanner wont know as its not been programmed to know. Ram Tah had to reprogramme the scanners so we could discover ruins, prior to that the scanner had know idea what it was looking at as it was alien to it.