I believe it has something to do with the C compiler. In my test, see eweasel test#melt080, I always get True regardless of the compilation mode.

Since we compile the code of the runtime where the byte code is interpreted, I'm not surprised that you get True, since my C compiler always reports True. 

In workbench and final mode, then your C compiler is producing a different answer. So which C compiler are you using and on which platform?