The flag is there for you to override if you think you know better. We don't answer questions or provide support for any use-case with the proprietary driver.
Refusing to run if a particular kernel module is loaded (even if you don't touch it at all) is overstepping. You should at least provide an override flag.
There is an override flag, its linked in the code snippet.
Use "--unsupported-gpu" or "--my-next-gpu-wont-be-nvidia" to bypass the check and allow sway to launch.