Is it by design that TextMesh Pro will only be batched when they are in Z-position=0?

Unity Engine
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1

I was having a weird experience that a simple UI with only vertex color Images and TextMesh Pro which create around 30 drawcalls. Looking into the issue and I found TextMesh Pro will not be batched and even break the Images batches between them when the Z-position of TextMesh Pro is not 0. Furthermore, UI Images will be batched even they are not in same Z-pos.

The image below is a simple test case to present the issue. Every object is a no texture image + a TextMeshPro. The first two objects have a Z-pos adjustment and you can see the image and TMPro can not be batched but the last 3 objects are fine. Tested on Unity 2019.2.18f1 and Unity 2019.3.0f6 with both TestMeshPro 2.0.1 and 2.1.0 preview 11

If no any Z adjustment everything goes fine. So this behavior is by design or there will be a fix?

5803456--613570--TMProDrawCallTest.png
5803456--613570--TMProDrawCallTest.png842×1327 122 KB

2

I believe this is a limitation of the Canvas batching system where it requires the object be co-planar with the Canvas.