I guess I have the answer to my question.

It seems the registry tweak just allows to interoperability between 64bit and 32bit in a "interface wise" mean.
So 32bit can still not be "hosted" in 64bit environment. And by hosted is kind of an ActiveX control or in this sense a "call" from a 32bit thread to a 64bit environment.
The reason why it works with .DebugMode = True is because as the main 64bit thread will run its own call.

So the benefits of that DllSurrogate registry tweaks are limited..