Does it really matter if the bezels are 1 inch or 10 inches? It’s a desktop computer, it’s not like you’re gonna bring it with you in a backpack. On the contrary, large bezels in the iMac allows for more airflow. Because of this the iMac is almost always silent, in contrast to the new MBPs which can’t even drive an external screen without the fans going crazy.
My MBP 16 doesn't increase fan noise with 2 x HD monitors plugged in. I can barely hear it in normal use.
I think the problem may be related to 4K displays which would undoubtedly tax the CPU & GPU more, requiring more cooling.