Scaling the character's root does not give the expected result when Optimize Game Object is enabled on a Humanoid rig (Inspector > Rig).
If Optimize Game Object is disbaled, scale works as expected.
(see attached OptimizeScale.gif)

repro:
-open project
-open OptimizeScaleBug scene
-in Inspector > Rig, enable Optimize Game Object (should have Left_HandJoint01 exposed as an extra transform)
-Click Play, scale the character's root (Willard_Multitake)... all good, character scale as expected.
-Stop.
-scale the character's root (Willard_Multitake)...
bug: character joints are not scaled as expected (see gif)

fixed in:

Changeset: 314689 (402535b46759) [animation][case 912273] Scaling root does not scale character with Optimize GO enabled
Branch: animation/dev