Why are there so many reports about MacBook 16-inch Fan Noise specifically when the mac is attached to an external monitor?

That is certainly your prerogative. I also recommend using this Apple feedback link to tell them why you made this decision:

https://www.apple.com/feedback/macbookpro.html

They will not see your concern here.

Apps can affect Mac performance, battery runtime, temperature, and fan activity - https://support.apple.com/HT203184

You're using more GPU when using a second display. Processing = heat = more cooling required.

About fans and fan noise in your Apple product --> https://support.apple.com/HT202179

This is the place to check for any active Apple service programs for hardware issues:

Apple Service Programs - Apple Support

Might wish to bookmark it.

But I've read a lot about this model specifically and I'm curious if this model has unresolved problems.

Some of what you have seen is very likely a typical response to hearing fans speed up. The computer's fans are thermostatically controlled and, when sensors fitted to many internal components detect higher than normal heat, the fans are signaled to turn on in response. The speed is variable depending on the need. That is the safest ways to protect internal components—automatically

It is no different that the air-handling system in many homes and offices. If the temps in the house get too high or low, the system comes on automatically and, if a forced-air system, the fans as well.

Yes, there are thing that can overheat a Mac notebook but they are user issues. This Apple article is quite good:

Keep your Mac notebook within acceptable operating temperatures - Apple Support

In addition to the causes mentioned there, anti-virus and so-called "cleaning" apps can increase temperatures. So can Chrome, especially if you leave if left running in the background. It never sleeps. So can running in clamshell mode on some models.

I regret getting this MacBook. The fan will run very loud when I have 3 tabs open in Safari (with or without monitor attached). I have been on the phone and text with tech support and I also took it into the Apple store. The guy that took it in agreed it felt warmer than normal but when I picked it up I was told that my MacBook was fine, it was a "powerful machine" and the fans will come on to prevent it from overheating. In other words, they were no help. I continue to have this issue and I just want to warn others.

morable wrote:

<snip> I'm curious if this model has unresolved problems.

No.