When I read the article, I didn't know it was written be Stephen Wolfram. It sounded like any other math/tech blogger. He'd played with these things when he was younger, similar to what many programmers have done. And he was excited to find something familiar on a public building. It sounded completely non-arrogant to me. I used to play with fractals and would be just as excited to see my familiar toy on a public building, even though I didn't discover them.
He didn't claim to have invented it, or that the building was designed in his honor. I think you have to be expecting arrogance to see it in this article.
I took that as talking about the moment he discovered rule 30 (just like I discovered it myself at one point in my life). It doesn't sound like he's claiming the be "the discoverer" of it.
On the other hand, he might very well be the actual discoverer, anyway.
He didn't claim to have invented it, or that the building was designed in his honor. I think you have to be expecting arrogance to see it in this article.