I understand you did not expect this behavior, however it is actually consistent with the physics in minecraft. It is behaving as it is supposed to, even if that isn't how you expected.
Please DO NOT "fix" this. This is cool. Having a new light source that doesn't require support, especially one that looks as interesting as this one, is a fantastic feature that adds visual appeal to the game. These objects are otherworldly. Let them defy gravity. They are not Torches.
I wonder if this is because they may have originally intended it as a ceiling fixture and then adapted its code to accept other directions as data values.