For the sake of simplicity, this issue can be reproduced with a Default Lit material with a constant Base Color of 1, a constant Metallic of 1, a constant Specular of 0, and a constant roughness of 0. Nothing else. As in, a material producing the basic level of raytrace reflectivity. Here:
It appears HDR/emissive colors get “overblown” when the color of the material is brighter, as you can see in the preview window. If I set it to a darker color like 0.1, it dims the raytrace reflection enough that emissive or HDR colors like the sky of the example forest scene in the preview window, or in my OP’s case the Sky Atmosphere, of course it also dims everything else so that’s not an answer. Here’s how that looks:
So, here’s the actual Sky Atmosphere color. Note, the clouds are unlit but their emissive level is between 0-1. This is important to note for the second screenshot showing the reflection:
It’s important to note because only the Sky Atmosphere is overblown in the reflection, when the Skylight is turned up to 8 intensity.
Turning the skylight intensity up doesn’t actually change the Sky Atmosphere’s visible brightness in the actual sky either. It’s somehow only causing it to look like overly bright HDR/emissive in raytrace reflections.
Again, for reference, here is the exact same reflective material but with the Skylight set to 1 intensity. It’s completely accurate, no problems whatsoever. Too bad I’d like to light my scene with a brighter skylight, huh?
