Nothing really special, but I wondered why create that new mechanism when one perfectly fine already existed.
It's also a question of style -- I don't like having to roll a save each time a critter is hit; and I don't like the idea of a creature that may die from any wound, whatever its hp left and the damage dealt by the attack, with a bad roll (nat 1).
Although the latter isn't much important in this precise case since a gorbel is not likely to be the BBEG in the climactic endgame fight; the former slow down combat a bit - a bad thing IMHO.
Of course, I can see why it's not a bug, but a feature, as instakill chance was probably the result researched; and it also allows people to kill a gorbel without "detonating" it, which may also be a side-effect wanted. The automatic "on the creature death, it goes boom" death throes would differ on these two point.
But if you forgive me, I find it a bit clunky.
Changing this to death throes would be a revision more than an errata, but well, I said it was not exactly an errata.
OT: I've just noticed that your avatar pic on Necromancer's boards is slightly resized, and that makes you look worried. It may be a browser setting thing, but it's funny.