Add improvement from Lua

[krisztiantobias]

I have this Civ6 Scout mod, which is great, but it would be lovely to use Sailor Cat's Watchtower Improvement mod and put down a watchtower if the user click the lookout button.
I can place goody huts from lua, but that's it, the others don't work:

ImprovementBuilder.CanHaveImprovement(localStartingPlot, IMPROVEMENT_SAILOR_WATCHTOWER, Game.GetLocalPlayer()) -- returns true
ImprovementBuilder.CanHaveImprovement(localStartingPlot, IMPROVEMENT_GOODY_HUT, -1) -- returns true

WorldBuilder.MapManager():SetImprovementType(localStartingPlot, IMPROVEMENT_GOODY_HUT, -1) -- works
WorldBuilder.MapManager():SetImprovementType(localStartingPlot, IMPROVEMENT_SAILOR_WATCHTOWER, -1) -- does not work
WorldBuilder.MapManager():SetImprovementType(localStartingPlot, IMPROVEMENT_FARM, 0) -- does not work
ImprovementBuilder.SetImprovementType(localStartingPlot, IMPROVEMENT_SAILOR_WATCHTOWER, Game.GetLocalPlayer()) -- does not work
ImprovementBuilder.SetImprovementType(localStartingPlot, IMPROVEMENT_FARM, Game.GetLocalPlayer()) -- does not work

Is there a limitation here or what? With ImprovementBuilder I can see the smoke animation for improvements, but that's it, it does not put off the improvement itself.

The deletion also works just fine:

WorldBuilder.MapManager():SetImprovementType(PlacedWatchtowers[i], -1, -1);