Was that a Deep South gardening show? I have a hard time believing that this plant can reach that size in zone 6 anywhere. Or are you April Fool-ing me?
I got this plant from a Holly Society of America (joint Great Rivers chapter and Tennessee chapter) meeting in 1992, in Memphis TN. It was donated to the plant auction, from Trees by Touliatos (Plato Touliatos, proprietor). It supposedly hails from the US National Arboretum's Lagerstroemia hybridization and trialing program. It was not one selected by the program to be named, but Plato's wife Sarah liked it a lot - and thus a plant is named and introduced.
So, I planted it at the Valley and enjoyed a couple seasons of growth and flowering - until January 1994 rudely introduced it to central KY reality at -28ºF. This was not 'Sarah's Favorite' temperature.
It was killed to the snow line (about 18 inches), but rebounded over the next couple years. It has never had to experience temps like that since (maybe -5 once since then) and has surged to heights in the 20 foot range. Maybe I'll take a measuring tape out there and see exactly. It flowers pretty heavily, and we've made dupes by rooting cuttings to have extras around the yard.