I would not expect to see labeling as a concept within classification.
I think the problem is that the tag wiki excerpt for labeling has been set as:
Annotating data on a map using text and/or graphics.
Annotating data on a map using text.
However, I think a better excerpt would be more like:
Rendering values from attribute tables as text on maps near their feature
This would seem to be in line with the definition of labeling at wiki.GIS.com:
Cartographic labeling is the craft of placing text on a map in
relation to the map symbols, together representing features and
properties of the real world. Using text effectively creates maps that
are clear, informative, and attractive. It is part of typography which
is an essential element of cartographic design.
I do not recall ever seeing a question tagged with labeling when I think they meant classification, or vice versa, but Labeling Excluded Data of Classification in ArcGIS legend? (which is the only question tagged with both) seems to be about the labels placed next to legend patches. Rather than getting into trying to distinguish feature labelling from legend labelling using a new tag perhaps we can just retag that question from labeling to legend.
This might lead to sentences in the tag wiki for labeling that include:
Use this tag only for feature labelling questions. For questions
about legend labels use the legend tag instead.
Applying that guideline suggests 65 questions that may need review.