Follow-up to this post. I decided to start a new post as I no longer consider the problem to be solved and would be thankful for further help.
Due to a mistake in the implementation, I previously believed that the issue was completely solved by disabling Metal API Validation. Although it helped a bit, the total additional memory consumption of the app after creating 1860 PSOs from a binary archive (even higher when compiled on device) is still about 180 MB, while the resource size per PSO in the Metal memory panel is about 2 KB. The measurements of the total increase were made in release mode, as shown by the Graphics HUD on iPad and Activity Monitor on Mac.
Any help regarding this problem would be greatly appreciated.