The overheating issue is the longest thread both here and on the official Apple forums for a reason. The issue is annoying as hell! And Apple isn't exactly being great with their customer service by just denying it's an issue.
They are not denying anything.
If you read carefully or if you have had the chance to interact with them directly, the correct wording is "it is expected".
So they do expect this to be a problem. They just won't do anything about existing machines. That's the difference.
I can live with my 16" in clamshell and I find the 16" a perfect machine elsewhere so... I'm good. It seems those of you who absolutely cannot work with just one monitor will need to pay for an eGPU or an upgrade to the new 5600M card.
So what else do you want? Apple has never publicly acknowledged any issue at all. Not even the butterfly keys that had much higher failure rate than this external monitor situation.