SingelChoiceAction with ItemType = ItemIsMode is shown as ItemIsOperation in the Tools group

Alex is right, the type of the created bar item depends on the action container's IsMenuMode property. If this property is 'True', the container treats all SingelChoiceActions as 'ItemIsOperation' regardless of their ItemType.
There are two ways to change the default behavior:

1. Customize a container using the ActionControlsSiteController.CustomizeContainerActions event:

C#
using DevExpress.ExpressApp;
using DevExpress.ExpressApp.SystemModule;
using DevExpress.ExpressApp.Win.Templates.Bars.ActionControls;

namespace dxT963770.Module.Win.Controllers {
    public class CustomizeContainerActionsController : Controller {

        protected override void OnActivated() {
            base.OnActivated();
            Frame.GetController<ActionControlsSiteController>().CustomizeContainerActions += OnCustomizeContainerActions;
        }
        protected override void OnDeactivated() {
            Frame.GetController<ActionControlsSiteController>().CustomizeContainerActions -= OnCustomizeContainerActions;
            base.OnDeactivated();
        }
        private void OnCustomizeContainerActions(object sender, CustomizeContainerActionsEventArgs e) {
            if(e.Category == "Tools") {
                ((BarLinkActionControlContainer)e.Container).IsMenuMode = false;
            }
        }
    }
}

2. Create a custom LightStyleMainRibbonForm and DetailRibbonForm templates as described at How to: Create a Custom WinForms Ribbon Template. After that, find the required 'barActionContainer…' (the 'barActionContainerTools' for the 'Tools' category) and change its IsMenuMode in the designer.

Thanks,
Anatol