To reproduce:
1. Open any project
2. Set up an object with Timeline's Playable Director
3. Enter timeline's Record mode
4. Add keyframes to Position or Rotation (only one of them, any adding method applies)
5. After recording try to change supposedly unrecorded Transform's Component (Rotation or Position)
6. Notice how the changed Component gets reverted back when previewing the recorded Clip indicating that both Position and Rotation were recorded

Expected: only selected Transform is being recorded
Actual: both Position and Rotation are being recorded (check video attached)

Reproduced in: 2017.1.4p2, 2017.2.3p1, 2017.4.5f1, 2018.1.6f1, 2018.2.0b11, 2018.3.0a3

Note: reproduces with either Position or Rotation keyframes. Seems they are linked, while Scale works as intended