How to reproduce:
1. Open the attached project ("2D_Instancing_Bug_-_2018.2.zip")
2. Open the repro scene ("SampleScene")
3. Open the Frame Debugger
4. Enter Play mode
5. Enable the Frame Debugger
6. Inspect the "Draw Mesh" calls

Expected results: Draw Mesh calls are instanced
Actual results: Draw Mesh calls are not instanced because "Non-instance properties set for instanced shader"

Reproducible with: 2017.4.31f1, 2018.4.5f1, 2019.1.13f1, 2019.2.0f1, 2019.3.0a11

Workaround:
Material Property Block values that are set by Sprite Renderer cannot be used with SpriteRenderer.GetPropertyBlock because they contain a texture property - _MainTex, which breaks instancing, even if this one texture is shared by consecutive draw calls. To work around this, material instances have to be created for each texture: at runtime copy materials for each texture/sprite and assign textures directly to material instance as _MainTex instead of MPB. Runtime changes to Sprite Renderer properties such as flip, color will also have to be manually monitored to update as you can no longer use GetPropertyBlock and update those values in a bunch.