Originally, we inserted a recentchanges row for each local page affected by a change in a connected wikibase repo (e.g. if the label of Q159 was used on 10000 pages, we inserted 10000 rc rows when that label was changed). However, this was found to generate too much load (see e.g. T171027), so a hard cut-off was introduced as a quick fix, see https://gerrit.wikimedia.org/r/#/c/383384/
That situation is however not satisfactory. We at least want to be smarter which pages to "ping" via the recentchanges mechanism - e.g. insert rc rows for the most watched pages that are affected by the change.