Pig, man. There is no overdrive on a manual transmission.
Now that makes more sense. The 4th gear used to be a separate unit in automatic transmissions, and they called it overdrive.
I just looked it up, and you are technically correct. They still call top gear overdrive in manuals even though it isn't a separate unit.
Turns out you were technically correct the first time, and both versions of the overdrive image are valid.