This is the first time I have encountered this word. I haven't read The Importance of being Earnest. I love the idea of a pre-existing excuse for cutting out early. The example of the blackbird "bunburying" by acting differently in city and country seems to draw an entirely different meaning from Wilde's text, it doesn't match the definition in the word of the day either, so maybe it is just a creative extension. Also cool.

I've never run into the word either, but now I have a name
for the fellow whose house I am helping to remodel for
the last few months.

Three years ago I had the pleasure of performing as Lane, the butler, in a production of Earnest directed by my eldest daughter, with her sister as one of my fellow actors.

I suspect that the author of the blackbird article was more concerned with drawing a comparison between bird and human behavior in an attention-getting way than he was in drawing an accurate parallel with the central definition of "bunburying." You're right, Fred (and welcome to the forum, by the way), the usage doesn't match the definition, but I imagine that Anu doesn't have many examples to draw from.