I think the question is “Will an automatic transmission last as long as a typical clutch?” I’ve read and re-read the OP a couple of times.
I agree that a well maintained manual transmission will completely outlive an automatic, the same cannot be said for the clutch. I’ve only had one car with the clutch lasting to 200K. Every thing else lasted 150K to 175K. And I have NEVER replaced the transmission. The longest lived, my Toyota P/U was at 325K miles when it was totaled. 2 clutches, but same original transmission. But, I have an automatic that has lasted 170K in my Ford Explorer with no sign of problems or slippage so far (knock on wood).