What exactly is the difference between plunging_neckline and center_opening?

I was under the impression that they were distinct, that center opening was for stuff which can be closed and plunging neckline was for stuff which can't.

But the number of posts marked as both is throwing me off. Is one a subset of the other, or something?

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I'll give two examples:

post #6064699 (S)
post #7996931 (S)

At present, both of these are tagged with center opening, which is not what I would have expected. I'm asking not only if that tag is appropriate in those two instances, but also whether there's a general rule to follow with this.

I use center opening on very large clothing cutout, which usually include cleavage cutout and stomach cutout. (like post #10869774)

Those wouldn't still just be clothing cutout, regardless of the size? I appreciate the answer, but I'm even more confused now.

In my opinion, center opening implies that there is a gap or hole in the center, either by being unbuttoned, partially unzipped, cleavage cutout or even another piece of clothing on top, like a capelet. There is something surrounding that gap.

While plunging neckline its more about the clothing design making a V-shape itself.

In your examples and wiki edits, I'd tag post #6064699 and post #10804482 with plunging neckline and remove center opening, the rest seems fine to me

looking at the posts i think center opening was supposed be inner sideboob...

there is some male focus posts in center opening too so maybe not

basically it's a mix of open clothes and cleavage cutout that is in the center instead of the top, partially unzipped clothes, etc.