Postmodernism isn't "philosophy", in the same sense that you wouldn't really say "the enlightenment" to be that either.

But semantic riddles aside, are you even still following what the point is?

I didn't say that "debates over authorial intent" can't be philosophy. Or that a work of fiction couldn't develop meanings that hadn't been foreseen.

But then that's not something you can use as a reference for any kind of serious objective question? You have examples because they are "starkly obvious" and help dispel ambiguities. If they are themselves an abyss of contention, what the hell are you even doing?

p.s. the ship of theseus is probably the more famous example you wanted to bring up