Example: You've been wanting to take cooking classes, but you've also been wanting to join an improv group. If you don't have time/resources for both of these projects, you might choose a "metaproject" like "weekly dinner party with funny friends" -- it doesn't strictly meet the requirements from either project, but might achieve something deeper you're looking for.

I have an impression that’s the only thing it actually does, right there in the last paragraph (but sure, it’s quite vaguely defined just by this single example).

It doesn’t really say much else, though - just a bunch of commonplace realizations that most of ideas never get done, and then some jump to “metaprojects”, possibly to reframe the frustrations so they feel less stressful, but I don’t get that part.