The normative text says "Headings and labels describe topic or purpose". I don't see how an icon can describe anything, and the Understanding page makes no mention of the use of icons as labels.
It has been stated that icons can be used as labels in discussions regarding SC 3.3.2: Labels or Instructions, which does not require that labels are accurate or descriptive. See #3276
If the use of icons as labels conforms with SC 3.3.2 but does not conform with SC 2.4.6, I think this should be made explicit in the Understanding pages for both success criteria.