The overcast HDRIs on Polyhaven's website look far too bright. Below you can see the HDR files. They should be in linear color space, so the blue sky looks correct to me. The overcast sky looks far too bright, and gets even brighter if you convert it from linear to sRGB.

Here are two examples:

https://polyhaven.com/a/overcast_soil_puresky
https://polyhaven.com/a/autumn_field_puresky
 

The overcast sky is supposed to look like this after tone mapping, but converting the above HDR image from linear to sRGB will only make it even brighter.

I also notice they list “EVs” on the item page. The blue sky uses 27 and the overcast sky is 12. Is that related?

Probably better luck asking them or some other community that uses HDRI backgrounds more like Blender community or other modelers.