Tagging for the renderer isn't "fixing" anything, particularly when you don't update the affected tags correctly. If there isn't physical separation between lanes in the real world, they shouldn't be mapped as separate ways in OSM.

I'm pretty sure I knew what I was doing when I remodeled this junction and do not appreciate having my work undone just to make it look prettier in OSM Carto.

Reverted in https://www.openstreetmap.org/changeset/163009296