The idea that the universe is discrete/computational is a fine idea, but underspecified and useless on its own. There's an infinite array of computable rules to choose from. But the fact that with a few assumptions on the rules you can then limit to both GR and QM is very non-trivial and, in my opinion, pretty surprising.
To your point, does it prove that this is _the_ correct theory? Definitely not, and metering language around the claims is important. Still, the result feels novel, surprising, and worthy of further investigation, alongside the other popular models being explored. I think it's a shame that Wolfram's demeanor turns people off from the work.
