How does reduced value works?

Once it has been in a bundle, there is no way to know if you got it from there or full price. Same logic for 0 value.

If they key for the game in the bundle doesn't expire then it still counts as bundled, If it worked like you're saying people would save the key for years until the game is back to FULL CV and everybody will abuse it. Doesn't matter if you want to give it as a steam gift or a key.

It was an attempt to prevent exploits of the CV system and it went as well as trying to extinguish a supercriticality with a bucket of water.

Forget about logic, since it's irrelevant here. Nothing ever gets removed from reduced or zero value. It can only go down in value, and it will be backdated. The only way to keep your CV is to have made it years ago, then you can keep it. If you're trying to build up CV level now, it can and will be reduced at any time and for any reason. Or it won't. You'll never know.