Metal in Photoshop Preferences>Performance? The app is still using OpenCL and Mercury Engine.
When I load Premiere or After Effects in the Activity Monitor you can see the Metal Compiler service running but not for Photoshop.
There is a setting ‘Use native operating system GPU acceleration’ but have never seen any performance or efficiency improvement with it.
The combination of
use: Use Graphics Processor to Accelerate
don't use : OpenCL or Use native Operating system GPU Acceleration
might cause the side effect o the the Adobe act to use the Apple Acceleration library. The explicit "use OpenCL" and "use native OS GPU " that Adobe makes the calls directly. Apple's library will possible switch to the "best option" given whatever hardware is present. ( i.e., knows better how to leverage Metal than the older Adobe code does).
As Adobe apps get more robustly skilled at taking advantage of Metal the "use native OS" switch should get better. Back when OpenCL was only option on macOS that should have been mostly redundant with the "use OpenCL" switch.
If that assumption is present in the Adobe code it will take time to unwind that uniformly everywhere. Apple's current position is that implies use of Metal shading language (and OpenCL deprecated). Adobe probably spent years building a taller OpenCL stack of tools and now Apple wants them to replace them all.