It looks like Epic added a reference to the lib causing the issue in the 5.4.x release:
https://github.com/EpicGames/UnrealEngine/commit/c1edfa3ade2c00540b9f0608e77dabac59c2a40e
Basically, they added a new module “MetalShaderCompiler” that rely on the libmetalirconverter.dylib provided by Apple, with the unauthorized function.
This seems to be something related to “Bindless Rendering” , in Experimental status.
This is on the 5.4.x branch. In earlier releases (5.3, 5.2, 5.1, 5.0) this dependency does not seems to be present. Are you sure you tested with earlier releases ?
Other than that, it is definitively possible this is a bug from Epic. I guess the only thing you may do for now is to report an issue.