Correct me if I am wrong: If you use steam console to download an old version of the game, regardless of currently installed version, steam downloads the whole game. Let’s say I was on v2.1, the game received an update v2.2 and I downloaded it normally through Steam, this downloads only the difference between 2.1 and 2.2. Let’s say I have 2.2, the game doesn’t use the “betas” feature and I want to downgrade the game. Steam ignores the current 2.2 install and downloads 2.1 in its entirety.
Correct me if I am wrong: If you use steam console to download an old version of the game, regardless of currently installed version, steam downloads the whole game. Let’s say I was on v2.1, the game received an update v2.2 and I downloaded it normally through Steam, this downloads only the difference between 2.1 and 2.2. Let’s say I have 2.2, the game doesn’t use the “betas” feature and I want to downgrade the game. Steam ignores the current 2.2 install and downloads 2.1 in its entirety.
Yes it downloads the whole game. But you’re overwriting the old one. Hence no significant shift in disk space used.