I wonder why the physicists are the only group to not want the full information released upfront? As a casual fan of physics[0] it seems like their completion of the standard model is possibly the biggest deal of all these breakthroughs, am I wrong?

[0]: PBS space time watcher

The writing is a bit ambiguous, but if I'm parsing it correctly it's only a big deal to the small subset of physicists who care about mathematical rigor: proof that Quantum Field Theory (i.e. what theorists have been using since the 1940s or so) is mathematically sound.

This part,

The existence proof pertains to the simplest grand unified theory that includes the gauge fields and fermions of the Standard Model

looks like a reference to SU(5) GUT from 1974:

https://en.wikipedia.org/wiki/Georgi%E2%80%93Glashow_model

Careful, completion of the standard model ≠ theory of quantum gravity or theory of everything. The actual question is too abstruse for me (biophysicist).