There clearly are multiple versions of the grenade/aoespell rules in the book, just like there's multiple versions of the troll/dwarf costs and a few more errors around. The example says A. The rules say B. They contradict, and there's evidence supporting either case. Given the fact the AoE spells themselves mention a threshold test and do not mention a dodge test in any way, it sounds like RAI was no dodge test, though the GenCon Agents might be more up to date with future intent or have gone for a temporal ruling awaiting an official one. But in Core, there are more pointers to no dodging than there are to dodging, even if they may change that in the future.
There is no Opposed Test when it comes to 'explosions', no matter whether they are technological or magical. The things pointing in the opposite are examples and tables, not written rules, so are more easily artefacts than the written statement of a threshold test. Occam's Razor sides with Bull's explanation from months ago, as much as I dislike it.Explosions do base damage which lessens over distance, Spells do damage based on how many hits they score above the 3 needed to place it without scatter, which is constant in the entire area.
Now apparently in GenCon they have been using a temporary ruling where a dodge test at a -2 penalty creates distance, since otherwise it's far too easy to create a total partywipe with grenades, and it means someone who gets really lucky on a dodge roll, or is a decent bit removed from the center, might totally avoid an indirect area spell. I like that quite a bit, though it begs the question of whether you can be aware of an AoE magic spell going off, and what happens if you do not spot the exploding grenade or realize an AoE spell is getting tossed your way.
The rules need errata to get rid of the artefacts, and in all fairness they need to do something about the lack of defense against AoE effects. But RAW does not support claims on dodging them more than support claims on not dodging them right now, and statements from multiple sources support the ruling you and I both dislike.