Question WatermarkRender spike in Profiler

This screenshot of the Profiler says everything: https://i.imgur.com/ZQEiOEG.png

Context:
I'm in the process of optimizing perf for my game. Started from scratch. Only thing left active in my hierarchy is a camera and directional light.

In 10 runs where the average ms per frame is 1ms, this is my first time seeing a 28ms spike for Watermark Render. I know that this the "Development build" watermark displayed in the bottom right corner of a dev build.

I know the watermark won't be there in a production build, but what hope do I have to optimize my game if I get poor performance out of a watermark when nothing else on the screen has to be rendered.

What could be the problem?

Screenshot of said build (a black screen because as mentioned I stripped out everything): https://i.imgur.com/fuVnUUv.png

Unity 2019.4.3f1
MacOS 10.14.6
2.3 GHz Intel Core i5
Intel Iris Plus Graphics 655 1536 MB

Build settings
- Platform: WebGL
- Development build: on
- Autoconnect profiler: on

URP render pipeline settings: https://i.imgur.com/uc6j1uM.png
URP renderer settings: https://i.imgur.com/d4D1add.png
Project settings
- Graphics: https://i.imgur.com/VBjcvau.png
- Player: https://i.imgur.com/E3aIcEk.png
- Quality: https://i.imgur.com/2Ks6sTz.png