So your argument is "map makers are retarded, so let's make it as hard as possible for them to fuck up". Cool.
It doesn't make sense for a sector effect that says DAMAGE (FIRE) to make the top of a water FOF solid, especially when it does jack squat to any other FOF type.
It's also dumb that when you want to make something like lava with the "wading" properties of slime, you have to make "fake lava", as people dub it, by using water damage to secretly turn the lava into slime.
It makes no sense to have three different elemental damage types which affect water blocks differently while having only one type of elemental protection. If you're going down that route, then just make all of the three simply "standard" elemental damage, give them all the same kill message (the nasty goop one would work fine), and change the differentiating factor to their effects on water blocks.
The current system we have is sloppy, nonsensical and very inelegant, and no matter what argument you use against me you're not going to change my mind because this is an implementation-level problem, not a practical one.
EDIT: Maybe we should split the Star Post into like 32 different things, the angle system is way too complicated for people to use.