Your tioga bar is stiffer for sure, but the amount of flex in the handlebar is negligible compared to the bending in the base of the stem that is amplified along the length of the entire stem/handlebar assembly and experienced as flex when pulling on the handlebars. This is exacerbated by the fact that the expander stem system is not designed to eliminate play fully, the tiniest gap between steerer and stem results in play since it's only the lowest portion of the stem that's wedged in place... it's really just not properly designed.