This article is fun to play 'spot the false dichotomy' and 'identify the hidden assumption' with!
Elon Musk isn't an expert in physics or philosophy, and we have literally zero reason to consider his opinion valid on anything but his space program or car companies, and that's only because he is likely speaking the words of experts that he hired.
It's like Stephen Hawkings talking about economics and fearing capitalism/automation. He is not an expert in economics, and has zero real backing for his claims.
The assumptions about this "one in a billion chance" assumes that a) it is possible to simulate a universe as large or larger than our own using the energy and material in our universe. b) that other universes are possible at all, which follow radically different laws of physics. Assumptions that, to my knowledge, have yet to be proven in any form.