Examples of cases and implementations where wglGetProcAddress() returns non-NULL on error?

The Load OpenGL Functions - OpenGL Wiki page states the following:

While the MSDN documentation says that wglGetProcAddress returns NULL on failure, some implementations will return other values. 1, 2, and 3 are used, as well as -1.

But unfortunately, it doesn’t provide any examples. Whereas this is a very serious question, since such values are simply not valid pointers in most environments. And this knowledge can be very useful for people and projects who implement their own OpenGL loading.

Could anyone please shed some light on this mystery?
Thanks in advance.

Examples of what? Of which particular implementations do this?

Yes, and in which cases they do that.