If you're flying from MSP, get the ETA even if it's not required. I was denied boarding for an itinerary---all on DL---that was eligible for China TWOV (the third country was Japan) because the redcoat insisted that everyone needed a visa for China and refused to check the actual requirements. I suspect MSP DL GAs are much more draconian on visa requirements than necessary. Anecdotally I've heard similar stories over the years. You don't want to be denied boarding even if you're right.