Note: the browser tests will need the reload to take place, so either we implement T246219: Reload page after saving+purging is done first or we temporarily reload in the browser test itself. (The former seems nicer – T246219 isn’t blocked on anything.)
It appears the wikitext as we already have it in our browser tests will do the right thing showing only the preferred statement once we implement the update edit decision (c.f. T238662), add a browser test for it, and assert its effect on the article.