System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 451.67

Blender Version
Broken: version: 2.90.0, branch: master, commit date: 2020-08-31 11:26, hash: rB0330d1af29c0
Worked: (newest version of Blender that worked as expected)

Short description of error
While editing an armature in pose mode x-ray will have no effect on other objects.
So only the armature whil be transparent, making x-ray in pose mode pretty much useless.

Just realized that x-ray has to be enabled in object mode before going into pose mode.

*Steps to replicate

1. Enabel x-ray in object mode
2. Select armature and go into pose mode
3. enable x-ray