"The Unreasonable Effectiveness of X" is a reference to the well-known 'the unreasonable effectiveness of mathematics in the natural sciences'. It's turned into some sort of meme. Maybe you've seen 'the unreasonable effectiveness of recurrent neural networks' before.
What you were referring to is a talk by a core developer at JuliaCon 2019 titled 'The unreasonable effectiveness of multiple dispatch' [1], which has less of a fanboy-vibe imho.
Edit: Oh. I didn't notice the arstechnica article had this exact title. That's a bit cheap...