I missed the thrust bearing focus too. But IMO the thrust bearing should have a residual oil film on it during start-up, just like any journal bearing in the engine has.
I'd bet the load on the crank thrust bearing with the clutch pedal depressed is less force than the force on a rod bearings when the engine first fires up. There would have to be a large lack of oil flow (constant zero oil pressure) to start causing damage. How does anyone know the rear thrust bearing is designed well and getting adequate lubrication while it's always running? Is the oil supply really pressure fed, or is it splash fed? Maybe they just wear out early from normal engine running due to design issues on that specific engine.
Doing a cold start-up in millions of cars all over the globe doesn't cause their journal bearings or crank thrust bearings to fail - meaning the residual oil film seems adequate for a second or two until oil flow starts moving.