When disabling bloom, usually in order to save a few more fps if possible, the sun is rendering as a perfectly outlined disk (with small atmospheric variation effect yet a plain disk). Furthermore, when Render Scaling is above 100%, the sun disk is rendering with a black outline (like many other “lights” by the way).
However when bloom is enabled, it is rendering as a fading disk expanding outward and it is very convincing, and when SS is above 100% it is no longer rendering with a black outline.
I understand the Bloom shader is actually making something like a blur on a smaller res copy of the render buffer and uses this as the highlighting source (it is usually how it works and why it takes some resources - read back, shader, blend). However it is not necessary to render the full Bloom Shader pass.
I’d suggest when Bloom is disabled, FS2020 renders the Sun disk with a fading out halo. It would just be a rendering shader, not a bloom shader, specifically for the sun, and this will greatly enhance the effect.