"Disable Player Theme Selection" works for single scenarios but not for campaigns

I've created a single-player scenario that has the player's theme locked to Red/Rhaskos/Rhaskos. I published the map locally and tested it out from the "Scenarios" menu, no issues - the player theme selection UI is not visible on the scenarios menu for this map, and the player's theme is locked to Rhaskos in the level itself.

However, I've added the map as the first level of a custom campaign I'm working on, and the player theme selection UI is visible on the campaign menu, which does affect the player's theme for the level despite it supposedly being locked.