From the article: "The issue is that with bundling the .dll, it would still mean it being extracted somewhere and writing additional code for the P/Invoke to work, and C++/CLI gets compiled to .NET IL code, in other words, you can open the resulting app in dnSpy and see the C++ code translated to C# equivalent (which is not what I want, I want native code)."

I don't understand what the author is talking about. When they say the C++ code will be translated to the equivalent c#, that's not how interop works at all... the native C++ DLL is not somehow made magically more vulnerable to reverse engineering because you can p/invoke to it.