See T76307 and T102086 for stakeholders to ask for input.

In fact Scope-increase is unused (and apart from spam/experiments never was)...

Scope-increase description:
Used in the context of sprints to mark tasks which were not selected at the sprint planning meeting but were added due to some emergency, unexpected dependency etc.
It provides a metric of how well the Scrum methodology works for a team and helps to keep track of the number of story points a team is able to do in a sprint according to plan.

Unplanned-Sprint-Work description:
Allows teams to track any work that enters a sprint after it begins.

(emphasis by me)

IMO the emphasized parts represent the same thing.

Per @Aklapper 's request ccing @Tobi_WMDE_SW, @Gilles, @Qgil, @Awjrichards, @Tgr, @Lydia_Pintscher for T76307: Add scope-increase tag for teams running sprints and @Spage, @JAufrecht, @mmodell, @K4-713, @KLans_WMF, @ksmith, @Awjrichards, @DStrine, @atgo for T102086: Create "Unplanned-Sprint-Work" tag for tracking unplanned work that enters a sprint.