[Vuejs]-Leaflet side by side always displays layers on the right

I’ve finally found this SE post
https://gis.stackexchange.com/questions/345096/leaflet-compare-two-side-by-side-geojson-layers

I had to create 2 panes:

this.map.createPane('left');
this.map.createPane('right');

And then for each GEOjson assign the correct pane:

const layer = L.geoJSON(map, { style: { color, weight: 2, opacity: 1 }, pane: 'left' }).addTo(this.map);

Thank god for this SE post. I was going crazy.