That’s the way it’s always been, on all platforms, until I changed the behaviour on OSX and Linux. Eventually I even changed it on the Windows case, but only with --rtdist.
The reason I don’t do it for the SDK build is because we ship the entire Python installation into a directory in the SDK installation, so makepanda will need to know where everything is. If we allowed it to pick up an already installed Python installation, we’re not really guaranteed to pick up the whole Python installation correctly if it’s a custom one, and there’ll also be a chance that it picks up installed site-packages and all that. Furthermore, many people will use a system-wide Python installation, which puts python2x.dll in the system32 directory, so we’d need to locate that one separately to make sure we pick it up.
So because makepanda relies on the exact location of files within the Python installation, it’d be too error-prone to allow it to pick up an arbitrary installation, not to mention the fact that the code to properly locate all the files would probably get rather hacky.
If you don’t agree though, we can certainly talk about changing this behaviour, if we properly document the intricacies involved.