“Also aggregate inline CSS” doesn’t seem to be doing anything

We’re trying to aggregate inline CSS – but even when that option is enabled, we’re still seeing all of the CSS from the customizer appearing inline. Am I perhaps misunderstanding what this feature does? I thought that would remove the CSS from being inline and add it to an external minified file.

Please let me know if you have any suggestions on how to optimize the CSS that comes from the customizer and is currently appearing inline.