Currently working on a project and having some annoying issues with pinching in my hdri, rotating it isn't working as expected unless I add a projection layer and change it to spherical, at which point I can rotate it on the appropriate axis to hide the pinching.
Got me thinking and I tried setting up the HDRI on a material with triplanar projection and colour correction and then I just copied the resulting layer and pasted it into the environment which worked a treat. Would be a lot easier to do stuff like this if we could see the node tree for the environment, as if it was a material.