AU: Desktop::setGlobalScaleFactor with value < 1 results in wrongly sized window

When running an AU that uses Desktop::getInstance().setGlobalScaleFactor(0.75) in Logic Pro X, the contents of the Plugin Editor GUI don’t fill the entire window. The same code works fine on Windows (VST3) with REAPER.

To provide some more context: I’m at the tip of develop (commit 83b1436c6a21f82ffdc4125592836f21dbd7b1e7).

This is what it looks like: