href is referring to the href attribute of a
<a> tag. We could debate about the need of having that tag, but it's not a synonym of the other tags.
Tag synonyms are created when two tags with the same meaning are used; they are also created when there are users who keep typoing a tag, for example writing druapl-view instead of drupal-views.
hyperlink, and links are synonym, and they should be merged.
I would keep links, and make the other one its synonym, but also doing the opposite would be fine with me.