I don't understand how people don't see this....

he either have control over the information or he doesn't. In the case of the former, it means by transitive closure that Putin would have the control as well.

It makes me wonder though who got the best deal - Chinese or Russians - i suppose each party was thinking that they are playing off the other.

You're ignoring the fact that what he does know would still have a great deal of value to some other intelligence services. Even if he can't give up a password, he still has years of first-hand experience, knowledge of specific programs whose documentation he chose to copy etc.

In other words, just because he doesn't have the key to the box doesn't mean he has forgotten everything about the contents, especially considering that he packed it.