Terrain draw instanced for WebGL builds

There is a draw instanced checkbox at the top of terrain settings that vastly improves render speed in the editor. I was hoping this would help my WebGL build where terrain is a huge bottleneck. However, the terrain does not render at all now.
Is this expected behavior with WebGL?
What is the instanced check box actually doing? If i cannot get it to work, perhaps i can emulate it for some partial performance improvements.

It does not seem to work on different computers or with different projects so i guess it is just broken in the version of Unity. 2019 does seem to work with a test project (although it introduces new failed build problems for me on my actual project).
Can anyone confirm that its definitely an issue with the Unity version - 2018.3
Can Unity confirm if the fix in 2019 will be back ported?

I think the best thing to do is submit a bug report.

Thanks Marco. I would have thought this would not help as they seem to have already found and fixed it in 2019 as it works there on the same test project. Unless the upgrade changed some defaults which happened to be the cause…
Will post a report and see what happens. Thanks!

This still is not fixed

Given how old this thread is, I’d need a new bug report to bring this up with the team! @snipshotmedia , can you open one and share the report with me?