Graphics Questions
Why does my AMD Radeon Pro 5500M w/ 8 GB of GDDR6 memory say Intel UHD Graphics 630 1536 MB?
MacBook Pro 16", macOS 10.15
Pro-grade MBPs have dual graphics. Your specs
MacBook Pro 16-inch - Technical Specifications - Apple
The integrated graphics usually run when you are on battery to conserve energy. The more powerful 'discrete graphics' generally are used when on wall power.
These Apple articles discuss dual graphics:
Set graphics performance on MacBook Pro - Apple Support
Find out which graphics processor is in use on your MacBook Pro - Apple Support