The impression I ended up with was that if it helps, it does the job within 30min., since further procedures are needed if it doesn't resolve by then.
You are correct that it sounds like you leave in the 0W-30 when you "return it to the customer." I wondered if that might be an error though. If the 0W-30 is so wonderful, why isn't it recommended for every oil change?
I also agree that once it is warm, the viscosity is the same. On the other hand, most wear is rumored to take place during cold starts.
It just seems there are reasonable arguments either way. I chose a conservative interpretation.