Sorry for the late reply.
I agree with splitting report_fatal_error and that the GenCrashDiaglot default should not be changed. A new function can be added to pass GenCrashDiaglot=false to report_fatal_error.
For ⚙ D150674 [RISCV] Set GenCrashDialog=false for various report_fatal_error calls in lib/Target/RISCV , the call sites that indicate user errors can be switched to the new function.