To reproduce:
1. Open my attached project
2. Enter Play mode - two animations playing
3. In Hierarchy, find ChangeThisToBone001 and rename it to Bone001
4. Enter Play mode - three animations are playing

Expected: animations are being played not taking root bone's name into account
Actual: animations are only being played if the object's root bone has the same name as FBX's root bone (check .gif and image attached)

Reproduced in: 5.5.5p2, 5.6.4p4, 2017.1.2p4, 2017.2.1p1, 2017.3.0f3, 2018.1.0b1

Note: changing bones in lower Hierarchy doesn't affect the final outcome