Steps to reproduce:

1. Open attached project
2. Open scene "Test"
3. In hierarchy, select Rotation GO and notice that it has Y rotation of 180
4. In scene view notice that one of the objects is facing the opposite way
5. Using rotation handle, rotate Y rotation of "Rotation" GO and notice that objects marked with Optimize game object receive twice as much of rotation as set

Reproduced with: 5.4.0b24
Not reproducible: 5.3.5p7, 5.4.0b23