If it was intended they would have said "you are a true dragon" in the feat. Age categories can just be fluff (oh, and all creatures have age categories). Giving them 12 age categories? Fluff.
True dragon? Fluff, at the time of the writing. Remember, there's never been a set "True Dragon" type with a specific set of attributes, like you have for "giant" or whatever. Dragons of Eberron wasn't even out yet (or had just been released, either way they didn't know about it). Being a True Dragon got you access to the Draconic Vampirism feat (in a book they likely hadn't read, and it's not very important anyway) and meant you could be on the recieving end of a Dragonpact bargain (a very minor thing). I doubt they even noticed the epic feats thing, but since most prerequisites on epic feats mean that ability doesn't do anything, in general "True Dragon" didn't seem to have much meaning. They just didn't realize Dragons of Eberron was making True Dragon a really meaningful thing.
Nobody is using the monster manual definition for True Dragons. Not...one...single....person.
It's come up a few times in the last few pages, either calling it a primary source on the topic or referring to the definition therein, actually.
It's in the OP.
True dragons are those dragons that advance through age categories.
i.e. True dragons are creatures of the dragon type that advance (gain hit dice) through age categories.
Advance, as in, the "Advancement" line of the MM. The part where it has age categories in the dragon section, and the definition of "Advancement" at the beginning where it talks about getting tougher, or whatever. Dragons are shown to advance through age categories. Kobolds (including dragonwrought kobolds) advance by character class, not age categories.
Not advance as in "get older." It's really simple, and pretty much posted two or three times on every page.
Nope, that creates contradictions. It means Kobolds are True Dragons for Dragonpacts and Draconic Vampirism, but not in other places. Furthermore, that's actually using the definition for Lesser Dragons from Draconomicon as the only source for what a True Dragon is... meaning it actually ignores part of Draconomicon too, namely the part that says True Dragons are those that get more powerful as they get older (which Kobolds do). So even within Draconomicon itself that means Kobolds are both Lesser and True... an impossibility, according to that same book.
So yes, complete failure to make a definition without contradictions.
Or, you could have a nice, clean definition from one primary source and call it a day. Oh, and it doesn't include DWK, sorry.
Ignoring half the definition in your own primary source, and ignoring all other sources as well, is hardly clean.
You wouldn't have that scenario, because when you determine whether a dragon is a true dragon for both purposes you look at the primary source, the Draconomicon.
Which says that True Dragons are those that gain power as they get older. DW Kobolds do. Whoops, you just ignored your own primary source. Remember, Draconomicon doesn't say "True Dragons are those that get more powerful as they get older, and advance through age categories." It says the first like about True Dragons, and then says that "other dragons" that don't advance through age categories are lesser. If the first applies but the second doesn't, you have a contradiction in the rules.
Technically speaking, draconomicon doesn't actually say that dragons must be either true dragons or lesser. It says that "those creatures which grow more powerful as they get older" are "true dragons".
It does, actually. It talks about True Dragons, and then it says "Other" creatures are Lesser. That makes the categories mutually exclusive.
As for a Half Dragon Kobold Druid 15: well, yeah, it seems it would be. One of the few places where Timeless Body is actually even vaguely useful. Funny that. Though I doubt that would ever come up. I wonder how many people have ever played a Half Dragon Druid at all, let alone a Half Dragon Kobold Druid. And to level 15?
JaronK