Actually I think I understand now. I do see this happening with events, but not with actions or data.
In general, when a certain category is selected, then changing what is selected from that section will update the project tree. You can see that by clicking an action from the project tree, then going to the Action Panel to select another action. Then you will see this second action selected in the project tree (I think this behavior is reasonable).

As to the actual problem, I'm not sure what's wrong since I see `this._selectedType = this.SelectedTypeEnum.PROJECT;` in the ProjectTree constructor.