The animation is in the tab content, not on the tabs.
You have to set SkinManager.AnimEffects.PageChange.Time to a non-0 number (300 seems a good value)
The atcFade mode will have an old behavior soon.
And other effects will be added also.
Animation may be controlled in the TsSkinManager component.
And animation may be disabled in the custom TsPageControl component, using the AllowAnimSwitching property.