The article mentions it's a halt-on-error pattern:
https://www.sandordargo.com/blog/2026/09/16/cpp26-trivial-in...
Edit: sorry, missed the UB bit.
One minor nit, it's not halt-on-error, it's restart-on-error since the watchdog then restarts the system. The technical term for this is rejuvenation and it's standard practice in SCADA and similar to deal with this-shouldn't-happen error conditions.
That's more why you would want them to be defined in the first place.
That says why they don't want it to be UB. The question, I believe, was why they want statically-known-infinite non-trivial loops to continue being UB.