I am curios why the nedarim-shevuot tag is a single tag.
The Mishnah separates them into separate categories.
The Mishna also puts Lulav and Sukkah in the same tractate even though we have them as separate tags. We aren't modelling the Mishna here. We're making useful groupings to help people find things on our site.
If there become enough different questions to make separate Neder and Shevuot tags useful, we can split it up. For now I don't see much benefit in doing so.