fusangite said:
Initially, I was surprised by the definition for "metaplot" for the purposes of this thread.
And I'm surprised by your surprise!

The use of the term metaplot in this context has been around for years; in fact, I've not only never heard another word used to describe the phenomena, I've also never heard another competing use of the word.
This isn't something that Paka came up with and the definition is thus a matter of debate; this usage of the word has made it's way through columns at rpg.net, gamingoutpost, and other places, as well as there being at any given time about five threads on the message boards (especially at rpg.net) decrying the practice for those (many) publishers who use it. The usage is old and established.
Besides, meta- doesn't mean "outside" or anything like that as you imply; your own coined phrase metatextual is likely incorrect, since I can't map it to any definition of the prefix meta- that I know, with the possible exception of definition six below. Meta- means:
- Later in time: metestrus.
- At a later stage of development: metanephros.
- Situated behind: metacarpus.
- Change; transformation: metachromatism.
- Alternation: metagenesis.
- Beyond; transcending; more comprehensive: metalinguistics.
- At a higher state of development: metazoan.
- Having undergone metamorphosis: metasomatic.
- Derivative or related chemical substance: metaprotein.
- Of or relating to one of three possible isomers of a benzene ring with two attached chemical groups, in which the carbon atoms with attached groups are separated by one unsubstituted carbon atom: meta-dibromobenzene.
I think definitions six or seven mean exactly what this phrase is meant to convey, and that whomever it was that first coined the phrase knew exactly what they were doing when they did so.
I think the only folks who are really bothered by it are those who are bothered on principle, and those who actually play in the setting and like to keep up to date on all the many supplements that a setting may have.
It doesn't bother me particularly because 1) I don't play in published settings anyway, or at least I don't run published settings and 2) even if I did, I'd not feel compelled to buy and integrate every supplement as it comes out. Certainly (as in FR) I wouldn't feel compelled to integrate novels as they come out...