Since the update to Factorio version 1.1 transport drones seem to ignore roads when on a space platfrom of the "Space Exploration" mod. It looks like they consider the platfrom plating as road tiles because they seem to move on a direct line from start to end. This only affects pathing, the movement of items itself ist still working as intended.
I'm also curious about this. Drones actually fly through the void if there are no platform at all, it's hilarious. Space drones! Put aside this funny behavior, I hope drones will be allowed in space platforms going forward.
I have found another interesting behavior: road tiles can no longer be built over with space platfroms and when removing road tiles in space they spawn normal earth tiles instead of "space".