Extended Range, implemented stupidly?

Browsing around, I found a description of ER that looked a bit flawed.

Apparantly target is checked, if its in normal range then spell goes off
as if normal.

If its NOT in normal range, then a second check is made to see if its in
extended range. If it is, spell goes off as extended range, if not,
then you just can't cast.

But here's the funny thing:

If you cast on a target which moves beyond range before the spell goes
off, then you fail. Which is fine of course.

Except that, due to the funny implementation, this means you can cast on
a target which is within normal range, but which moves out into extended
range, so you get a spell failure.

To see how funny that is, imagine two mages with similar gear, casting
on two targets; one is in normal range but moving away, the other is out
at the far end of extended range. Mage one casts and gets a fail,
because his target has moved out of normal range, meanwhile mage two
hits, because his target was in extended range all along...even though
its noticably further away than the one Mage one failed to hit!

Range isn't actually that big a concern for my mage most of the time,
but thinking back, this effect messed up my cleric's CHeals a time or
two and I never understood why; the guy I was trying to heal was moving
in and out of extended range, never out so far as to be past ER, now I
get why I'd nonetheless sometimes get odd results!