With unreliable allies becoming reliable, the 4 or more element rule is clunky because of the various ways it can be achieved.
That is, you do it not just by breaking enemy commands, but also by simply destroying elements. It's the comparative sum of losses achieved by these various ways which determines whether the unreliable command becomes reliable. Here are some examples:
1. My reliable troops destroy 5 elements, and I lose 1 element in the process.
2. Your command of 12 elements breaks, and you destroy 8 elements of mine without breaking any commands.
3. I break your command of 12 elements, and you break a command of mine with 8 elements.
Does this make sense?