The rule is in effect for the ladder that you are opped on for not being in the top 25 partly due to the fact that upholding the rules can get dicey in those positions, for one. For Two, defending that position could, not necessarily would, take time away from helping to keep the ladder running smoothly and helping new people.
As for the being in the top ten on another ladder the higher up staff believe that the time it takes to defend the ranks in the top ten would take time away from that person doing their op duties in a timely fashion.
mrskoala/Serena