What you're missing is, that's not automatic. That's telling you what's possible. The Rams would have to choose to structure his contract in that way. These articles are not telling you the details in how this stuff works.
I just went to Overthecap and created an estimated contract using their calculator with the goal of freeing up $10M in 2020. They would have to reduce the 2020 salary down to the vet minimum and give him a large signing bonus. The effect of that though would be to create very large cap hits in the years 2021 to 2025 (assuming a 5 year extension). Nothing Demoff has ever done suggests that they would make that choice.
You're going by what's possible; I'm going by what's probable based on the Rams history in managing the cap.
