Why would Apple configure MacBook Pro to use inferior graphics card when a better one is installed? The symptom of this was freezing streaming that Apple Support took 1.5 hours to diagnose and another hour to attempt to fix. 

Apparently, MacBook Pro 16" 2019 comes with two graphics card: the advertised ATI Radeon and an integrated one by Intel. ATI Radeon is supposed to be much better; thus MacBook Pro is advertising it; why do they have the integrated one I don't know. 

Anyway, my brand new MacBook (Catalina) was setup to use the integrated graphics card, while the more powerful ATI Radeon was staying idle, doing absolutely nothing. As the result it's freezing for a fraction of a second every few minutes.

Did anybody else see this? If you have a MacBook Pro, and in About This Mac / System Report / Graphics/Displays see multiple graphics cards, which one is used by MacBook, according to About This Mac / Graphics?

More importantly, is it possible to reconfigure which one is being used? Apple Support tried things such reinstalling OS, which changed absolutely nothing.
MacBook Pro has come in models with both an integrated and a discrete graphics processing unit for many years now.

The integrated graphics uses less energy than the discrete GPU, so in order to maximize battery life, it is used whenever possible.

The integrated graphics should be plenty powerful to play ordinary YouTube videos or play a DVD, which are the tasks you describe in your linked question. Unless you have an external monitor connected to the MacBook Pro, the integrated graphics should handle this fine.

However, you can definitely configure your MacBook Pro to use the discrete graphics. This way you can test whether or not the problem goes away when using the discrete graphics.

You can the setting by opening System Preferences > Energy Saver, and removing the checkmark from the "Automatic graphics switching" checkbox. When this checkmark is removed, the computer will use the discrete graphics at all times.

Read more about it in Apple's documentation: 

https://support.apple.com/en-us/HT202043