Cel shading refers to a specific type of 3d rendering aims to mimic 2d texture. You would assume that's what the tag is for. But the wiki then points at how "cel shading" is also used for 2d animation now, suggests that the tag is used for the lighting and proceed to give a mixture of 2d and 3d examples. That's very confusing and problematic because:
1. While there are similar terms for 2d animation, they didn't come from cel shading. Quite the opposite, cel shading is named after the traditional 2d coloring process using celluloids. You can at best say that this is an ambiguous term used for two things. And wikipedia does use "cel shading" for the 3d rendering style.
2. We already have anime coloring for the 2d coloring style.
3. Some of the posts there wouldn't even fit anime coloring necessarily. While they are still layer-based and budget-saving, the number of layers a gacha game illustration has is still much more than an average anime. Either we put them both under the same tag, create a new tag, or don't tag gacha cels at all because people can't recognize them anyway.
4. We don't have a tag for actual cel shading.