And thus demonstrated is the value of lots of different implementations of a spec. Already one hole found in the spec in just this article, and I'm sure there will be/were more.
Multiple independent implementations are crucial for the long-term health of the web platform, so we're trying to do our part! :)
It's really great that you're doing this work. This principle also applies to many other specs. I've implemented a few and found multiple issues with real-world impact.
The browsers may have been written to "work" / not crash over adhering strictly to the spec.
At least Chromium has integrated multiple different fuzzers into their regular development workflow and found lots of bugs even before going public.
That's a bit of a... non-sequitur. Imagine if you had tweeted "eggplants are my favorite vegetables", someone corrected you "actually they're fruits", and then you declared: "And thus demonstrated is the value of Twitter! Someone already made me a better-informed citizen in response to my tweet." This feels kind of similar.
This isn't to say what they're doing isn't valuable, or that there isn't value in having lots of implementations of a spec. Just saying that implication isn't there (yet) with this particular example.