Paraphrasing Alan the lead developer from the mailing list:
For CSS this is the PropertyName setting in Bundles → CSS → Settings. Currently it is scoped to ‘meta.property-list.css -meta.property-value’ which should limit where it fires.
Looking in [the SCSS bundle], it there is a Smart Typing Pairs setting with the pair which is scoped to source.css. This appears to be wrong, and it should instead mimic the CSS bundle wrt. only enabling it in the context where it makes sense.
To do that, just set your Bundle Editor
→ SCSS
→ Settings
→ Smart Typing Pairs
→ Scope Selector
to
meta.property-list.scss -meta.property-value