When the lightLevelRenderThrough option is set to true and the light level overlay enabled, not only the light level overlay renders through blocks but shapes as well.

The same happens to structures, regardless of what the structuresRenderThrough option is set to.

I took a look at the code and it seems like a simple case of forgetting to call the postRender() method of the parent class. Calling it fixed the issue for me.
https://github.com/drzewiec123/minihud/commit/c32008cacea5f63081d80684d94530464e2b56a8
I thought about creating a pull request, but I'm not sure which branch it would be best to merge to.

I'll just add it directly, kinda less hassle that way for a one-liner. I'm not doing any more releases for anything older than 1.19.2 currently, until the 1.12.2 development code gets ported forward at some point.