System Information
Operating system: Windows-10-10.0.18362-SP0 64 Bits
Graphics card: GeForce GTX 1060 3GB/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 445.87

Blender Version
Broken: version: 2.82 (sub 7), branch: master, commit date: 2020-03-12 05:06, hash: rB375c7dc4caf4
Worked: (optional)

Short description of error
Parenting a pre-painted Grease Pencil object to Armature doesn't work.

Exact steps for others to reproduce the error
Create new project
Create GP Object, draw 2 squiggles, create 2 vertex groups, assign each squiggle's verts (weight of 1) to each separate group. (Same as creating VG before drawing squiggles with Add Weight Data enabled)
Create Armature with 2 bones named the same way as the vertex groups.
Set Armature as GP's parent with Armature Deform
Moving bones in pose mode doesn't move the squiggles.

This works however if I use With Empty Groups which makes no sense compared to when you rig a mesh.