He may have, but it's not as like we knew Manning was going to be pardoned in 2013. She was also put through extremely cruel and unusual treatment during detention, such as being kept in solitary confinement for months at a time for no reason other than to make an example.
Unless you're involved in that decision making process and leaking the information here, that's just pure random guy internet speculation. The scope for them was very different and you're basically saying "trust this with your life, you'll be totally fine".
What is this based on? No matter what people think he deserves, my guess is that Snowden, like Assange, is a character that the ruling class wants to make an example of. Chelsea Manning does not threaten the ruling class, especially after you know what.