Perhaps. I’ve not looked at the generated code before, but it seems in the class.generated files BlueprintNativeEvent generates the exec and implementation declarations while BlueprintImplementableEvent only generates the function name declaration. In the intermediate project.generated file both UFunctions are constructed almost identically (FUNC_Native flag missing from a BlueprintImplementableEvent) and are found on the calling UObject by name, which is shared with the base class’ UFunction.
Certainly it makes sense to specify them BlueprintNativeEvent in the first place to avoid any possible issues.