This seems like a bad design - when I explicitly pass something to a function I expect it to be honored and not overwritten by some global state, especially one that can come from an environment variable.

I'm not even sure how a hint or a null parameter makes sense at all here since the program will be responsible for passing the shaders in the correct format (which isn't even checked outside of debug mode lol). There also doesn't seem to even be a way for the application to check what shader format is supported by the mystery device it was handed against its wishes, outside of getting the name and then mapping that back to supported shaders which may or may not change in the future.

Having two entry points for device creation with widly different argument types (one using flags, one using string-based properties with comically long names you might find the Java world) is also not something I would have expected in a newly designed API - that kind of uglyness is usually the result of changing requirements that the initial entry point did not forsee.