I can confirm and the reason is there isn't any material defined for the strokes and it's using the default material. I will try to explain why is happening this.

When you draw an stroke and the object hasn't materials, a default material is used with No Fill. When you use the Fill tool, it's checked if the material has fill enabled (or the tool would do nothing visible). As you haven't any material, a new material is created in the object with the fill enabled and it converts in material 0 (first slot of materials) and it's automaticatically used for any stroke that hasn't materials (your hand strokes). As result of that, the strokes of the hand now are using a material with fill, and this is what you see.

To solve the issue, just create a material for the strokes to avoid the default use of the first slot.