In the article End Condition Rules, item 3 says "Priority is only considered for end conditions attached to the same point."
Let's say I have the usual cut and fill end conditions running off of my ES and another end condition running off of, say, the EP. The usual end conditions on the ES have priorities of 10 and 20. If the EP's end condition has a priority of 9 or less, it will be solved before either of the ES's end conditions; if it has a priority of 11-19, it will be solved before one but not the other; if it has a priority of 21+, it will be solved only after the ES's end conditions.
This becomes relevant when the EP's end condition depends on the ES's end condition solutions, or vice versa.
Perhaps this specific scenario isn't realistic, but surely the point gets across, and it is most definitely relevant in complex end-condition scenarios.