is this a bug or is this intended? Because of this, queens cannot remotely spawn larva and nexus cannot remotely chronoboost buildings. The buildings must be clicked on screen or on the minimap and this seems counterintuitive to the improved UI of SC1.

The fix to wireframe casting is intentional and will not be reverted in the foreseeable future. The designers really like the idea of having the player need to get back to their base and take care of these special abilities instead of being able to control them remotely while looking elsewhere. Hopefully, this will give the player a better feeling of actually managing their base, rather than just clicking pictures on your hotkey bar or selection frames.