Thanks, just fixing my own mistake :) I'd broken it a few changesets before in #174938202 https://osmcha.org/changesets/174938202 while splitting up a landuse multipolygon into finer chunks, and somehow missed that the VT boundary also used the same way. JOSM's validator didn't catch it somehow, perhaps because the relation wasn't fully downloaded (although it usually warns on modifying an incomplete relation too which would have flagged the issue, so not sure what happened there). In any case, all fixed.
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            Published using OSMCha: https://osmcha.org/changesets/175006399
            