Comment by kens

The main reason was the "inhibit recovery problem". The inhibit line required a large current that went through all the cores. This caused electrical noise, requiring a delay while the noise settled down. Doing away with the inhibit line thus helped performance. The drive lines are also shorter, which also helps performance.

The paper "2 1/2 D High Speed Memory Systems: Past, Present, and Future" explains this, but not entirely clearly: https://ieeexplore.ieee.org/document/4038821